转：Python for delphi教程
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tutorial - Andy's Python Delphi Tutorial - Getting started with the basics. Also use these techniques if you are using Delphi 5 or below, and Python 2.0 or below. Includes info on getting these free components. |
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code - Here are Andy's Extensions - a delphi unit that adds a few utility functions to Python for Delphi. |
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tutorial - Here is a later tutorial using the Latest Techniques in Python for Delphi - use these if you have Delphi 6 and Python 2.1 or higher. |
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discussion & tips - Here is a discussion and tips on python for delphi deployment issues. |
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animated slideshow tutorial - Here is an animated visual viewlet demo of using the Python for Delphi components to build a Delphi app that talks to python. |
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example and screenshot of a Delphi GUI application which uses python code for all its business logic. |
return to main Andy Patterns home page
Introduction and Tutorial
Introduction
Create classes in python and have Delphi use these classes as if they were native Delphi classes! Benefit: python can do all the business logic and hard work, whilst Delphi can be used for the GUI and application framework etc.
The interactive shell and fast development time in python makes building business logic here. Define your domain classes and build all the units that do work. Only use Delphi for GUI.
On the other hand, if you want python to talk to and control delphi, then use COM.
Installation
Install Python for win32 Official distribution installer 
Then install the Python for Delphi components from
http://www.multimania.com/marat/delphi/python.htm
- Python for Delphi is a set of components that wrap up the Python 1.5 Dll into Delphi. They let you easily execute Python scripts, create new Python modules and new Python types. You can create Python extensions as Dlls and much more, including being able to create classes in python and have Delphi use these classes as if they were native Delphi classes!
so you finish up with the following palette:
which are the engine, the atomEngine, pythonDelphiVar, etc. Note: You only need to use about three of these components to do most of your python-delphi work, the rest are mostly historical or very advanced.
Basic Use - A simple test
A simple Python evaluator:
- Create a new Form
- Drop a TMemo (or a TRichEdit)
- Drop a TPythonGUIInputOutput
for displaying Python's messages - Drop a TMemo for the source code
- Drop a TPythonEngine
- Connect the attribute IO of the
TPythonEngine to the
TPythonGUIInputOutput. - Connect the attribute Output of
TPythonGUIInputOutput to
the TRichEdit. - Drop a TButton and
call it "Execute script" - Double-click on the button and add:
PythonEngine1.ExecStrings( Memo1.Lines );
- Write in the Memo1: some python code e.g. print 2+2 or
that pictured below - Click on the Execute button
click the button and
python is working with Delphi at a rudimentary level.
The above demonstration is an example of sending strings of code to the python interpreter and receiving Python standard output. You can drive python in this way as much as you like, by pumping text commands to it
PythonEngine.ExecStrings( commandLines )
The above Delphi component wrapper method is not always convenient, since ExecStrings expects commandLines to be a TStrings type, whereas sometimes you want to send a single string to the python interpreter / engine (and not have to create a stringlist) So I wrote a wrapper procedure PyExe (see AndysPythonDelphi extensions) which just takes a string. You can also send multiple lines to PyExe by separating lines with #13 (carriage return) or linefeed.
procedure PyExe(cmds: string;
engine: TAtomPythonEngine);
So that you can do things like:
PyExe('print 5');
PyExe('print 5+23'+#13+'print "welcome"');
// note two commands here
Controlling where Python standard output goes
Every Delphi form must have a PythonEngine component and a PythonInputOutput component.
There are two types of 'PythonIO' components - one that directs all output to a memo or richEdit, or you can use an IO component which lets you define a custom event handler to handle the python output. You can redirect output to raize codesite or even to the standard Delphi Debug Event Log Window: e.g.
- Create a new form, add a PythonEngine component and a PythonInputOutput component.
- Wire them together (Python engine's IO property to point to the PythonInputOutput component)
- Redirect all python standard output to the standard Delphi debug console, by double clicking on the PythonInputOutput component's OnSendData event and putting in the code OutputDebugString( PChar(Data));
PythonDelphiVars
To communicate between Delphi and Python at a deeper level we use the Delphi PythonDelphiVar component. It is a piece of Delphi that the python interpreter / engine can actually see! It looks like this:
The most important PythonDelphiVar component property is VarName property which is the name by which python 'sees' this component.
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The Name property of the PythonDelphiVar component is, of course, how Delphi refers to the PythonDelphiVar component. |
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The VarName property of the PythonDelphiVar component is how the Python side refers to the PythonDelphiVar component. |
In the picture above, from Python's point of view, I have called the PythonDelphiVar component VAR1 which means we can write Python code like:
PyExe('VAR1.Value = 101');
or in a python script, just simply
VAR1.Value = 101
which results in the PythonDelphiVar component having a value of 101. Delphi can access this component's value with
PythonDelphiVar1.ValueAsString
TIP: In practice, I use the convention of making the name of each PythonDelphiVar component and its VarName property the same.
Example #1 - Running an entire python program and storing the results in a set of PythonDelphiVar components.
All Delphi does is trigger off the script (say when a button get hit) and then retieves the results from the PythonDelphiVar components.
The Delphi side:
- Create a new form, add a PythonEngine component (name it PE) and a PythonInputOutput component. Wire them together as previously discussed in controlling where the Python output goes to, above.
- Drag down two PythonDelphiVar components and name them HEADERVAR and RESULTVAR. Set the VarName properties to the same as their names.
- Create a button with the code:
procedure TForm2.Button2Click(Sender: TObject);
begin
PyExeFile('unit2.py', PE);
end;
The Python side
- Create a python unit called unit2.py and put it in the same folder as your delphi units. Add the following code to the python unit:
print "Welcome to Python unit2" HEADERVAR.Value = '----- Welcome -------' RESULTVAR.Value = 200 * 3
Now run the delphi form and press the button. Our PythonDelphiVar components should be populated. How do we know?
- Just add another button with the code:
procedure TForm2.Button3Click(Sender: TObject);
begin
showmessage( HEADERVAR.ValueAsString
+#13+ RESULTVAR.ValueAsString );
end;
Example #2 - Loading an external python program and calling a function in it, storing the result in a PythonDelphiVar component.
The Python side
Modify the unit2.py python script as follows, to include a function which takes a comma separated list of numbers and returns the sum of those numbers. The result is stored in a PythonDelphiVar component named RESULTVAR.
import string
def calcAvg(str):
total = 0
vallist = map(lambda n: int(n), string.split(str,','))
for val in vallist:
total += val
RESULTVAR.Value = total / len(vallist)
The Delphi side:
procedure TForm2.FormCreate(Sender: TObject);
begin
PyExeFile('unit2.py', PE);
// this loads in the python class
end;
procedure TForm2.Button4Click(Sender: TObject);
begin
PyExe('calcAvg("1,5,10")', PE);
showmessage( RESULTVAR.ValueAsString );
end;
Now add an enhancement where, on the Delphi side, you allow the user to type in the list he or she wants to calculate the average on. Add an edit component and a button with the following code.
procedure TForm2.Button5Click(Sender: TObject);
begin
PyExe('calcAvg("' + edit1.text + '")', PE);
showmessage( RESULTVAR.ValueAsString );
end;
yields 13. Success!
Direct access to Python Classes
First we used stdout to communicate between Delphi and Python.
Then we used special pigeon holes ( PythonDelphiVar components ) to communicate between Delphi and Python.
Now we are going to learn how to gain access to actual Python classes and instances, and call the methods of those instances using normal Delphi dot notation. And of course being able to set and get properties of those instances would be cool too, wouldn't it?
Using TPythonAtom
Basically the technique is to define, in Delphi, some OleVariant variables which hold references to Python objects. We can then access methods and properties on these python objects using the familiar dot syntax that we use in Delphi (and most other languages) e.g.
pythonicCustomer.Address := '23 Smith st.' ; pythonicCustomer.RunReport() ;
Official documentation on this technique is found in Demo12 of the examples that come with the Python for Delphi components. "Simply add the PythonAtom in the uses clause, declare a new var of type OleVariant and call the function getAtom( any Python object ). It will return a new OleVariant that will let you access properties or methods very simply, as you would do with Word !" See also latest features. Note: if you don't understand the preceding paragraph, that's ok, since you won't have to know about PythonAtom in the next examples, because I have wrapped the difficult stuff up in a simple function or two.
The Delphi side:
- Create a new form, and drag down the pythonAtomEngine component and name it PE. Drop a TPythonGUIInputOutput for displaying Python's messages. Connect this to your richtext or memo component. More info on redirecting python IO earlier in this article.
- Add AndyDelphiPy, ComCtrls, pythonAtom units to your uses clause, e.g.
implementation uses AndyDelphiPy, ComCtrls, pythonAtom; var aCustomer : OleVariant;
- Then in the formshow or formCreate event add the code that loads the main unit of your python code..
procedure TfrmMain.FormShow(Sender: TObject);
begin
PyExeFile('YourPythonApp.py', PE);
At this point the python interpreter has loaded and executed your python classes and any code in the unit you are loading. Now we can create instances of python classes in Delphi and store the references to them in variants.
aCustomer := PyClass('Customer()', pdv, PE);
The above code shows how to instantiate a python class Customer and store that reference in a Delphi variant aCustomer.
The pdv is a necessary intermediate python delphi var used for the instantiation and is not used subsequently. Drag and drop a PythonDelphiVar component and name it "pdv" (the pdv simply stands for python delphi var) and set the Varname property to "pdv" [ ASIDE: ** Matthew Vincent. suggested during the talk that I could perhaps create this pdv component within my PyClass wrapper function, thus eliminating the pdv parameter from the PyClass function. I couldn't get this to work, as the pythonDelphiVar component seems to need to be created at design time - creating it at runtime with the form as the owner worked, but didn't actually satisfy the python engine. Even if this would have worked, we would still have to specify the owning form as a paramter to PyClass, which means we would have gained nothing in terms of the number of parameters we would have had to pass.... ]
Note also that the PyClass delphi function is another one of the AndysPythonDelphi extensions which simplifies the process of instantiating a python class from Delphi. Normally you have to deal with a couple of lines of code and some reference counting, in order to instantiate a python class. By using my wrapper function PyClass the process is reduced to a simple one line call.
- When this particular example delphi app runs, after the execution of the FormShow event, the customer instance will have been created and will be ready to be used. Let's add a button so that we can manipulate that instance. Create a button and add the following code:
aCustomer.Surname := 'Bloggs' ;
aCustomer.Address := '23 Smith st.' ;
inc( aCustomer.NumOrders );
showmessage( 'Customer info: ' +
aCustomer.RunReport() );
That's it for the Delphi side of things.
The Python side:
Now let's work on the python side of things, which only involved creating a single python unit named YourPythonApp.py in the same folder as your delphi app.
class Customer:
def __init__(self, surname=''):
self.Surname = surname
self.Address = 'unknown address'
self.NumOrders = 0
def RunReport(self):
return 'Customer ' + self.Surname +
' of ' + self.Address +
' has made ' + `self.NumOrders` +
' orders so far.'
Note that the method __init__ in the above class is the constructor method (like .Create in Delphi).
Running the Delphi app and clicking the button should give you:
Success!
Passing python objects as parameters
Your Delphi code can now interact seamlessly with python objects. One last thing to watch out for is the situation where your delphi code passes a python instance around as a parameter to other python methods, you cannot simply pass the variant reference e.g.
aCustomer.AddOrder(anOrder) # won't work
instead you must pass the pure python reference. So define a python method in each python class called something like 'myself' e.g.
class Order:
...
def myself(self):
return self
then you will be able to successfully:
aCustomer.AddOrder(anOrder.myself) # works
If you are lucky, you may only need to define the 'myself' function just once, perhaps in some Python base class. And of course you can call the function anything you like, just don't call it 'self' since that already reserved by both Delphi and Python.
Deployment
Easy - no registry settings or anything fancy.
As well as your compiled delphi executable, just add the python dll (only about 500 k) in the folder containing your app, plus a Lib folder containing any extra python units you are using. For example random.py and whrandom.py could be placed into the Lib folder if you had used them. The examples used in this article did not use any extra units (the string unit that we used for string.split is a "built in" unit and so does not need to be supplied with your app).
plus
Advanced topic: Here is a discussion and tips on python for delphi deployment issues.
Andy's helpful minor extensions to Python-for-Delphi
These are Andy's extra high-level wrapper functions used and described in this article. These functions use and augment the standard Python-for-Delphi components.
More info on python
If you need further informations on Python, visit the official Web site at http://www.python.org/
Andy's Easy Tips on Reading Python Code
Python is a simple, straightforward and elegant language. It uses standard conventions of accessing methods and properties and is fully OO. Types are associated with objects not variables, so you don’t need to declare variables. Functions are called like afunction(param1, param2) and objects are created from classes the same way e.g. o = MyClass(). Python is case sensitive.
There are no begin end reserved words or { } symbols in Python to indicate code blocks – this is done through indentation. The colon in if lzt: simply means ‘then’. The idiom of testing objects (rather than expressions) in an if statement makes sense as python treats empty lists, None and 0 as false.
Python understands named parameters e.g. In a method call, afunction(From=None) means you are passing None (null / nil) as the ‘From’ parameter, whilst in a method definition From=None means that if the caller does not supply this parameter, then it will default to None.
The first argument of all methods defined inside classes must be ‘self’. This argument fills the role of the reserved word this in C++ or Java or self in Delphi. Most languages supply this parameter (a reference to the current instance) implicitly whereas Python makes this concept explicit. At runtime this parameter is supplied by the system, not the caller of the method, thus the def AddOrder(self, order) method in reality takes one parameter when calling it: AddOrder( order ).
The statement pass means do nothing.
You can return multiple items at once e.g. return (2, 50) and also assign multiple items at once e.g. x, y, z = 0 or even expressions like result, status, errmsg = myfunction(1, 90).
Other class files/modules are imported using import somefile. __init__ methods are simply constructors. Finally, a lambda is just a one line function that reads functionname = lambda paramlist : returnedexpression.
Both Python and JPython (Java Python, now called Jython) are open source, free and available from http://www.python.org/
:-)
Related 'Python for Delphi' Links on this site:
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tutorial - Andy's Python Delphi Tutorial - Getting started with the basics. Also use these techniques if you are using Delphi 5 or below, and Python 2.0 or below. Includes info on getting these free components. |
|
code - Here are Andy's Extensions - a delphi unit that adds a few utility functions to Python for Delphi. |
|
tutorial - Here is a later tutorial using the Latest Techniques in Python for Delphi - use these if you have Delphi 6 and Python 2.1 or higher. |
|
discussion & tips - Here is a discussion and tips on python for delphi deployment issues. |
|
animated slideshow tutorial - Here is an animated visual viewlet demo of using the Python for Delphi components to build a Delphi app that talks to python. |
|
example and screenshot of a Delphi GUI application which uses python code for all its business logic. |
return to main Andy Patterns home page
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Andy's helpful minor extensions to Python-for-DelphiThese are Andy's Delphi wrapper functions used and described in this article. Save the following Delphi code as AndyDelphiPy.pas and use this unit as necessary
unit AndyDelphiPy; interface uses Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, PythonEngine, AtomPythonEngine, Rzcsintf, ComCtrls, pythonAtom; procedure PyExe(cmds: string; engine: TAtomPythonEngine);
procedure PyExeFile(fp: string; engine: TAtomPythonEngine);
function PyClass(pyclass: string; pydelphivar : TPythonDelphiVar; engine: TAtomPythonEngine): OleVariant;
function PyVarToAtom(pydelphivar : TPythonDelphiVar; engine: TAtomPythonEngine): OleVariant;
procedure PyConsoleOut(const Data: String);
implementation procedure PyExe(cmds: string; engine: TAtomPythonEngine);
var
s: TStringList;
begin
s := TStringList.create;
try
s.text := cmds;
engine.ExecStrings( s );
finally
s.free;
end;
end;
procedure PyExeFile(fp: string; engine: TAtomPythonEngine);
var
s: TStringList;
begin
s := TStringList.create;
try
if pos(':\', fp) = 0 then
fp := ExtractFilePath(Application.ExeName) + fp;
s.LoadFromFile( fp );
engine.ExecStrings( s );
finally
s.free;
end;
end;
function PyVarToAtom(pydelphivar : TPythonDelphiVar; engine: TAtomPythonEngine): OleVariant;
var
v: PPyObject;
begin
v := pydelphivar.ValueObject;
result := getAtom(v);
GetPythonEngine.Py_XDECREF(v);
end;
function PyClass(pyclass: string; pydelphivar : TPythonDelphiVar; engine: TAtomPythonEngine): OleVariant;;
begin
PyExe(pydelphivar.VarName + '.Value = ' + pyclass, engine);
result := PyVarToAtom(pydelphivar, engine);
end;
procedure PyConsoleOut(const Data: String);
begin
OutputDebugString( PChar(Data));
end;
end.
Related 'Python for Delphi' Links on this site:
return to main Andy Patterns home page
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Related 'Python for Delphi' Links on this site:
return to main Andy Patterns home page
Latest Python Delphi techniques & developmentsAs of October 2001 a totally new way of talking to python we developed, within the Python for Delphi framework. You use variants, and get smart references to python objects. So whilst before you could create a reference to an instance to a class, in an olevariant. Now we use variants. Also we can instantiate classes directly (without needing to use my PyClass() function etc. etc. Here is what Morgan, one of the authors of the components has to say:
The latest way of programming in python for Delphi if you have Delphi 6 and python 2.1 or higher.-Andy Bulka. These techniques are demonstrated in Demo25 in the examples folder of your Python for Delphi distribution. The old vs. the new ways.Because Delphi 6 has custom variants, they can point to specific smart proxies for python objects. Before Delphi 6, you could have an oleVariant pointing to a python instance, but you couldn't do the smart things like know that it was a list type etc. The following examples assume you have a module called LoginMgr.py in the python path or in the same folder as your application .exe that you have built in Delphi. Note that the python file LoginMgr.py contains within it a python class called LoginMgr which has a method called somemethod.
Note that it it possible to slightly mix the old and new way, so that if you use the AndyDelphiPy.PyExeFile('LoginMgr.py', PE); to import the module then you can then switch to the new way, declare an obj: variant; then instantiate an instance using obj := MainModule.LoginMgr(); However you still need Delphi 6 and so you might as well just use the new way properly. WidestringsDeclare your delphi strings widestrings if you want to get more than 255 chars back from calls to python methods that return strings. e.g. var BooleansIf your python method call returns 1 or 0 and this is supposed to be interpreted as a boolean, then cast it inside Delphi e.g. if Boolean( mypythonclassinstance.somemethod()) then
....
Accessing syspath directlyHere is a function that accesses a global variable called SysModule and access the syspath directly. This function also calls VarIsPythonSequence which tests to see if the parameter passed is a list or not. procedure TForm1.Button2Click(Sender: TObject);
const
LIB = 'E:\\ZopeWebSite\\bin\\lib';
LIBDLL = 'E:\\ZopeWebSite\\bin\\DLLs';
var
re : variant;
m : variant;
begin
memo1.lines.Add('SysModule.path is ' + SysModule.path);
memo1.lines.Add('');
Assert(VarIsPythonSequence(SysModule.path));
displaySysPath(ListBox1);
if not Boolean(SysModule.path.Contains(LIB)) then
SysModule.path.insert(0,LIB);
SysModule.path.append(LIBDLL);
memo1.lines.Add('SysModule.path now is ' + \
SysModule.path + #13#13);
displaySysPath(ListBox1);
fixSysPath; re := Import('re');
showmessage(re);
m := Import('xml.dom.minidom');
showmessage(m);
end; Playing with sys pathsThis is an example of how to set the python system path as seen by delphi's instance of the python interpreter (as represented by the pythonEngine component). Note that it is imperative that you have \\ as the slashed in your path as otherwise things like \fred will actually be interpreted as \f (whatever that escaped character is) plus 'red'. Technique 1procedure TForm1.fixSysPath; const LIB = 'E:\\ZopeWebSite\bin\\lib'; LIBDLL = 'E:\\ZopeWebSite\\bin\\DLLs'; begin // this is illegal // SysModule.path.Clear; // this will work with latest python for delphi components OK. //SysModule.path := NewPythonList; // this is a boring but effective solution as well.
while SysModule.path.Length > 1 do
SysModule.path.pop;
SysModule.path.append(LIBDLL); SysModule.path.append(LIB); end; Technique 2procedure TForm1.btnClearSyspathToJustLibClick(Sender: TObject); var currdir, libdir : string; begin currdir := ExtractFilePath( Application.ExeName );
libdir := EnsurePathHasDoubleSlashes(libdir); libdir := currdir + 'Lib'; SysModule.path := NewPythonList; // Relies on Jan 2002 install of python for Delphi components SysModule.path.append(currdir); SysModule.path.append(libdir); end; NOTE: See the python for delphi deployment section for a more in-depth discussion of paths. Supplimentary utility to display the python syspath in a delphi gui control.procedure TForm1.btnDisplaySysPathClick(Sender: TObject); Writing a Delphi function that uses a python function to do the hard work.Here is an example of writing a delphi utility function that takes a string, and splits it up (delimited by comma) and puts the result into a delphi list box. We are using python split function to do the splitting - cool eh? procedure TForm1.splitAstring(str:string; lstbox: TListBox);
var
s, lzt : variant;
i : integer;
begin
s := VarPythonCreate(str);
// convert normal string into a python string.
lzt := s.split(',');
for i := 0 to lzt.Length-1 do
lstbox.Items.Add(lzt.GetItem(i))
end;
Displaying the python syspath in a delphi listboxEven though we have a pointer to a python list object (via a Delphi variant), we still have to call .GetItem(i) on a python list rather than the python syntax of lzt[i] - why? Because we are in Delphi and thus we cannot use python syntax. procedure TForm1.displaySysPath(lstbox: TListBox);
var
lzt : variant;
i : integer;
begin
Assert(VarIsPythonSequence(SysModule.path));
lzt := SysModule.path;
for i := 0 to lzt.Length-1 do
lstbox.Items.Add(lzt.GetItem(i));
lstbox.Items.Add('----------------------------------');
end;
Loading python base64 and minidom module and processing XML in Delphiprocedure TForm1.minidomLoadClick(Sender: TObject); var m, doc, top : variant; s : string; begin fixSysPath; displaySysPath(ListBox1); m := Import('base64');
showmessage(m);
s := m.encodestring('this is some text which I am going to encode then decode again.');
showmessage(s + #13+#13 + m.decodestring(s));
m := Import('xml.dom.minidom');
doc := m.Document();
showmessage(doc);
top := doc.createElement( 'Workspace' );
top.setAttribute('Version', '1.1 beta4');
doc.appendChild(top);
s := doc.toxml();
showmessage('doc.toxml()' + #13+#13 + s);
end; Importing your own classEnsure you have a TPythonAtomEngine or TPythonEngine onto your form or datamodule. var mymodule, obj: variant; begin mymodule := Import('LoginMgr');
obj := mymodule.LoginMgr();
obj.somemethod() // call the method
Morgan's original tutorial on the new techniquesVarPyth unit:It wraps a Python object and lets you act on it (call methods or use properties) like you would do in Python, and like you did with PythonAtom, but there are differences: the variant always maintains its link to a Python object, and is never casted to a basic variant type (integer, string, array) when returning a value, like it was with PythonAtom. v1 := VarPythonCreate(1); v2 := VarPythonCreate(2); v1 + v2 will return a new variant that will hold the a Python object that is the result of the addition, and the addition will be performed by Python itself, using the PyNumber_Add API. Previously, with PythonAtom, if you accessed a property or called a method, the value returned by Python was automatically converted to a basic variant type, or wrapped up into an PythonAtom variant otherwise. The main advantage of this solution was to convert Python sequences (lists or tuples) into array of variants, letting us access them using the index operator (list[x]). Now, it is not possible anymore, as the returned sequence will be returned as a new custom variant, and our custom variant doesn't support indexing!!! I don't know how to do it? Maybe adding the flag varArray to our VType and setting array bounds that let us access any item, but I'm not sure... Anyway, it could work with sequences, but not with dictionaries, as it So, to work around this problem I added several special methods/properties: foo.GetItem(index): same as foo[index] foo.SetItem(index, value): same as foo[index] = value foo.Length or foo.Length(): same as len(foo) foo.GetSlice(index1, index2): same as foo[index1:index2] foo.SetSlice(index1, index2, value): same as foo[index1:index2] = value foo.Contains(value): same as value in foo foo.DeleteItem(Index): same del foo[index] Note that my special methods are not case sensitive. Note also that you must use the parenthesis with functions or methods that have no argument, to distinguish your call with a property access: list.sort() if you write list.sort only, you'll get the instance method object instead of performing the sort action. The advantage of the new solution is that you always work with the Python objects, and you can do anything you want with them, like you would in Python. The arithmetic operations, or comparisons, work the same, and you can't add an integer to a string, for instance, as you can with variants. v1 := VarPythonCreate(1); v2 := v1 + 'hello'; --> Python exception but v2 := 'hello' + v1; will work as the string is a variant that forces the right operand to be casted to a string variant, letting the concatenation to apply. But v2 := VarPythonCreate('hello') + v1; --> Python exception
And v2 := v1 + 'hello'; --> Python exception as hello is converted to a Python variant and then an addition is beformed between a number and a You can write also: v1 := VarPythonCreate([1, 2, 3]); v2 := v1 + VarPythonCreate([4, 5, 6]); --> you'll get: [1, 2, 3, 4, 5, 6] There are several facility functions that let you test the different types of Python objects, or that let you import other Python modules, or access the None object. Now, you can easily execute a Python script and then access the global vars of the main module: GetPythonEngine.ExecString('x = 2');
ShowMessage( MainModule.x ); // will display 2
you can access the sys module with the function SysModule, or you can import any module with the Import function, that returns the imported module object. myModule := Import('myModule');
myModule.foo(bar);
You can create a Python variant with: v := VarPythonCreate(myPythonObjectPointer);
v := VarPythonCreate(1);
v := VarPythonCreate('abc');
v := VarPythonCreate(3.14);
v := VarPythonCreate(True);
v := VarPythonCreate(VarArrayOf([1, 2, 3]));
v := VarPythonCreate([1, 2, 3]);
v := VarPythonCreate([1, 2, 3], stTuple);
v := None;
v := NewPythonList;
v := NewPythonList(3);
v := NewPythonDict;
you can access to the Python object pointer stored in the variant with ptr := ExtractPythonObjectFrom(v); you can test the variant with: VarIsPython(v) VarIsSequence(v) VarIsMapping(v) VarIsNumber(v) ... you can check if 2 variants shares the same Python object with VarIsSame(v1, v2) you can check if an instance has a class that is or inherits from a class with: VarIsInstanceOf(AInstance, AClass) or you can check the inheritence between 2 classes with VarIsSubclassOf(ADerived, AClass) Note that these 2 functions requires Python 2 or later. You can check None with: VarIsNone(v) or v = None or VarIsSame(v, None) You can instanciate a class like you would in Python: v := MainModule.MyClass() Note, that your class object must the property of a container and can't be stored in a variant: cl := MainModule.MyClass; // cl refers to MyClass v := cl(); // won't work because Delphi refuses to compile it! You can cast a Python variant to another type any time simply by assigning it to a variable of the required type or by forcing the cast with: if Boolean(list.Contains(1)) then ... So, I hope these explanations will help you understand better the new approach. Feel free to give your comments... Morgan
Demo25Here are some choice extracts from demo25 (from the Demo25 folder that you get when you download the Python for Delphi components), which show how to use this stuff: Playing with lists and dictionariesprocedure TMain.btnTestSequencesClick(Sender: TObject); var a, b, c : Variant; begin // initialize the operands // you can either use the overloaded function with an array of const // or use the VarArrayOf function that returns an array of variants that will // be casted to a Python list. a := VarPythonCreate([1, 2, 3]); Assert(VarIsPython(a)); Assert(VarIsPythonSequence(a)); Assert(VarIsPythonList(a)); Assert(a.Length = 3); // this is a special property that does the same as: len(a) in Python Assert(a.Length() = 3); // this is a special method that does the same as the special property Assert(len(a) = 3); Assert(a.GetItem(0) = 1); // this is a special method that lets you do the same as: a[0] in Python Assert(a.GetItem(1) = 2); Assert(a.GetItem(2) = 3); Assert(String(a) = '[1, 2, 3]'); b := VarPythonCreate(VarArrayOf([4, 5, 6])); Assert(VarIsPython(b)); Assert(VarIsPythonSequence(b)); Assert(VarIsPythonList(b)); Assert(b.Length = 3); Assert(b.Length() = 3); Assert(len(b) = 3); Assert(b.GetItem(0) = 4); Assert(b.GetItem(1) = 5); Assert(b.GetItem(2) = 6); Assert(String(b) = '[4, 5, 6]'); // concatenation c := a + b; // check result of operation Assert(String(c) = '[1, 2, 3, 4, 5, 6]'); // check that operation did not change the content of operands. Assert(String(a) = '[1, 2, 3]'); Assert(String(b) = '[4, 5, 6]'); // now with a litteral: note that with D6 SP1, we can't // concatenate a custom variant with an var array of variants c := a + b + VarPythonCreate(['Hello', 'World!', 3.14]); Assert( String(c) = '[1, 2, 3, 4, 5, 6, ''Hello'', ''World!'', 3.1400000000000001]' ); c := a + VarPythonCreate(['Hello', 'World!', 3.14]) + b; Assert( String(c) = '[1, 2, 3, ''Hello'', ''World!'', 3.1400000000000001, 4, 5, 6]' ); c := VarPythonCreate(['Hello', 'World!', 3.14]) + a + b; Assert( String(c) = '[''Hello'', ''World!'', 3.1400000000000001, 1, 2, 3, 4, 5, 6]' ); // multiplication c := a * 3; // in Python the multiplication of sequence concatenates n times the sequence Assert( String(c) = '[1, 2, 3, 1, 2, 3, 1, 2, 3]' ); // comparisons //------------ // equal c := a = b; Assert(c = False); c := a = a; Assert(c = True); Assert( String(a) = '[1, 2, 3]'); // not equal c := a <> b; Assert(c = True); Assert( not (c = b) ); c := a <> a; Assert(c = False); Assert( String(a) = '[1, 2, 3]'); // greater than c := a > b; Assert(c = False); c := b > a; Assert(c = True); Assert( String(a) > '[1, 1, 1]'); // greater or equal than c := a >= b; Assert(c = False); c := b >= a; Assert(c = True); c := a >= a; Assert(c = True); Assert( String(a) >= '[1, 2, 3]' ); // less than c := a < b; Assert(c = True); c := b < a; Assert(c = False); Assert( String(a) < '[4, 4, 4]'); // less or equal than c := a <= b; Assert(c = True); c := b <= a; Assert(c = False); c := a <= a; Assert(c = True); Assert( String(a) <= '[1, 2, 3]'); // copy c := a; Assert( c = a); Assert( VarIsSame(c, a) ); // checks if 2 variants share the same Python object. // sequence methods: c := b + a; c.sort(); // note that you must you the parenthesis to distinguish the // call between a method or a property. Assert( c = (a+b) ); c := NewPythonList; // facility for building sequences Assert( not VarIsTrue(c) ); // c is false because it's an empty collection c.append(1); c.append(2); c.append(3); Assert( VarIsTrue(c) ); // c is true because it's not an empty collection Assert(c = a); Assert( c.pop() = 3 ); Assert( String(c) = '[1, 2]'); c := NewPythonList(3); // facility for building sequences c.SetItem(0, 1); c.SetItem(1, 2); c.SetItem(2, 3); Assert(c = a); c.DeleteItem(1); Assert(c = VarPythonCreate([1,3])); Assert(VarPythonCreate([1,2,3,4]).GetSlice(1, 3) = VarPythonCreate([2,3])); // same as x = [1,2,3,4]; x[1:3] Assert(VarPythonCreate([1,2,3,4]).GetSlice(1, Ellipsis) = VarPythonCreate([2,3,4])); // same as x = [1,2,3,4]; x[1:] Assert(VarPythonCreate([1,2,3,4]).GetSlice(1, -1) = VarPythonCreate([2,3])); // same as x = [1,2,3,4]; x[1:-1] c := VarPythonCreate([1,2,3,4]); c.SetSlice(1, 3, VarPythonCreate([7, 8, 9])); Assert( c = VarPythonCreate([1, 7, 8, 9, 4]) ); Assert( Boolean(c.Contains( 7 )) ); // same as 7 in c Assert( not Boolean(c.Contains( 77 )) ); c.DelSlice(1,3); Assert( c = VarPythonCreate([1,9,4]) ); c := VarPythonCreate([1, 2, 3, 4], stTuple); // test a tuple
Assert( VarIsPythonTuple(c) );
Assert( VarIsPythonSequence(c) );
Assert( c.GetItem(1) = 2 );
Assert( c.Length = 4 );
c := NewPythonTuple(3);
c.SetItem(0, 1);
c.SetItem(1, 2);
c.SetItem(2, 3);
Assert( VarIsPythonTuple(c) );
Assert( VarIsPythonSequence(c) );
Assert( c.GetItem(1) = 2 );
Assert( c.Length = 3 );
// Done!
Log('Sequence test was Ok.');
end;
procedure TMain.btnTestMappingsClick(Sender: TObject);
var
a, b, c, keys, values : Variant;
begin
// initialize the operands
a := NewPythonDict;
Assert(VarIsPython(a));
Assert(VarIsPythonMapping(a));
Assert(VarIsPythonDict(a));
a.SetItem( 'a', 1 );
a.SetItem( 'b', 2 );
a.SetItem( 'c', 3 );
Assert(a.Length = 3);
// this is a special property that does the same as: len(a) in Python
Assert(a.Length() = 3);
// this is a special method that does the same as the special property
Assert(len(a) = 3);
Assert(a.GetItem('a') = 1);
// this is a special method that lets you do the same as: a[0] in Python
Assert(a.GetItem('b') = 2);
Assert(a.GetItem('c') = 3);
b := NewPythonDict;
Assert(VarIsPython(b));
Assert(VarIsPythonMapping(b));
Assert(VarIsPythonDict(b));
b.SetItem( 'd', 4 );
b.SetItem( 'e', 5 );
b.SetItem( 'f', 6 );
Assert(b.Length = 3);
Assert(b.Length() = 3);
Assert(len(b) = 3);
Assert(b.GetItem('d') = 4);
Assert(b.GetItem('e') = 5);
Assert(b.GetItem('f') = 6);
// copy c := a; Assert( c = a); Assert( VarIsSame(c, a) ); // checks if 2 variants share the same Python object. // dict methods
Assert( Boolean(a.has_key('a')) );
Assert( not Boolean(a.has_key('abc')) );
keys := a.keys();
keys.sort();
Assert( keys = VarPythonCreate(VarArrayOf(['a', 'b', 'c'])));
values := a.values();
values.sort();
Assert( values = VarPythonCreate(VarArrayOf([1, 2, 3])));
c := a;
c.DeleteItem('a');
Assert( not Boolean(c.has_key('a')) );
// Done!
Log('Mapping test was Ok.');
end;
playing with objectsprocedure TMain.btnTestObjectsClick(Sender: TObject);
var
_main, f : Variant;
val : Integer;
_folder, _str : String;
_myModule : Variant;
begin
PythonEngine1.ExecStrings(Memo2.Lines);
_main := MainModule;
Assert( VarIsPythonModule(_main) );
Assert( VarIsPythonModule(SysModule) );
Assert( Import('sys').version = SysModule.version );
Assert( Boolean(SysModule.modules.has_key(GetPythonEngine.ExecModule)) );
// if __main__ in sys.modules
Assert( VarIsSameType(_main, SysModule) );
Assert( _type(_main).__name__ = 'module');
Assert( BuiltinModule.type(_main).__name__ = 'module');
Assert( VarIsPythonClass(_main.Foo) );
Assert( VarIsPythonCallable(_main.Foo) );
Assert( VarIsPythonCallable(_main.Foo) );
Assert( VarIsTrue(BuiltinModule.callable(_main.Foo)) );
Assert( VarIsPythonInstance(_main.f) );
Assert( VarIsSame(_main.f.__class__, _main.Foo) );
Assert( VarIsPythonMethod(_main.f.Inc) );
Assert( VarIsPythonCallable(_main.f.Inc) );
Assert( VarIsTrue(BuiltinModule.callable(_main.f.Inc)) );
Assert( VarIsPythonFunction(_main.Add) );
Assert( VarIsPythonCallable(_main.Add) );
Assert( VarIsInstanceOf(_main.f, _main.Foo) );
Assert( VarIsTrue(BuiltinModule.isinstance(_main.f, _main.Foo)) );
Assert( VarIsSubclassOf(_main.Bar, _main.Foo) );
Assert( VarIsTrue(BuiltinModule.issubclass(_main.Bar, _main.Foo)) );
Assert( not VarIsSubclassOf(_main.Foo, _main.Bar) );
Assert( VarIsInstanceOf(_main.b, _main.Foo) );
Assert( not VarIsInstanceOf(_main.f, _main.Bar) );
Assert( VarIsTrue( BuiltinModule.vars(_main).has_key('f') ) );
Assert( VarIsTrue( BuiltinModule.dir(_main).Contains('f') ) );
f := _main.Foo(); // new instance of class Foo
Log('Instanciate class Foo: ' + f);
f.Inc(); // call a method without any arg, because there's a default arg.
f.Inc(2); // call a method with one arg, overriding the default arg.
Assert( VarIsPythonNumber(f.Value) );
Assert( VarIsPythonInteger(f.Value) );
Assert( f.Value = _main.f.Value ); // compare the result with what we did in the script
Assert( f.GetValue() = _main.f.GetValue() );
// compare the result with what we did in the script
Assert( VarIsPython( f.GetSelf() ) );
Assert( VarIsSame( f.GetSelf(), f ) );
Assert( BuiltinModule.getattr(f, 'Value') = f.Value );
// cascading calls
Assert( f.GetSelf().GetSelf().GetSelf().GetSelf().GetValue() = _main.f.GetValue() );
Assert( Boolean(f.__dict__.has_key('Value')) );
Assert( VarIsTrue( BuiltinModule.hasattr(f, 'Value') ) );
_str := 'Value';
Assert( Boolean(f.__dict__.has_key(_str)) ); // check with a string var
Assert( Boolean( BuiltinModule.hasattr(f, _str) ) );
val := f.Value;
f.Add(f); // passing itself as an argument
Assert( f.Value = val*2 );
// check param order
f.SetABC(1, 2, 3);
Assert(f.A = 1);
Assert(f.B = 2);
Assert(f.C = 3);
// add a property to an instance
f.Z := 99;
Assert(f.Z = 99);
// add a var to a module
_main.Z := 99;
Assert(_main.Z = 99);
// check none
Assert( VarIsNone(None) );
Assert( VarIsNone(VarPythonCreate([1, Null, 3]).GetItem(1)) ); // Null is casted to None
Assert( VarIsNone(VarPythonCreate([1, None, 3]).GetItem(1)) );
Assert( VarIsNone(f.Inc()) );
Assert( f.Inc() = None );
Assert( not Boolean(None) ); // if not None:
Assert( not VarIsTrue(None) ); // if not None:
Assert( Boolean(f) ); // if f:
Assert( VarIsTrue(f) ); // if f:
// call a function
Assert( _main.Add(2, 2) = 4 );
// importing an external module and using it
// first, extend the path with our current folder
_folder := ExtractFilePath(Application.ExeName);
if (Length(_folder) > 0) and (_folder[Length(_folder)] = '\') then
Delete(_folder, Length(_folder), 1);
if not Boolean(SysModule.path.Contains(_folder)) then
SysModule.path.insert(0, _folder);
// import the module
_myModule := Import('MyModule');
// call one of his functions
Assert( _myModule.Add(2, 2) = 4 );
// delete module var f
_main.__dict__.DeleteItem('f');
Assert( _main.__dict__.has_key('f') = False );
// open a file using Python
if FileExists('MyModule.py') then
begin
f := BuiltinModule.open('MyModule.py', 'r').readlines();
with TStringList.Create do
try
LoadFromFile('MyModule.py');
Assert( len(f) = Count);
finally
Free; // TStringList
end; // of try
end; // of if
end;
Related 'Python for Delphi' Links on this site:
return to main Andy Patterns home page
accessing delphi-form by pythonscript inside delphi-application It wraps a Python object and lets you act on it (call methods or use Previously, with PythonAtom, if you accessed a property or called a method, The main advantage of this solution was to convert Python sequences (lists Note that my special methods are not case sensitive. Note also that you must use the parenthesis with functions or methods that The advantage of the new solution is that you always work with the Python But v2 := VarPythonCreate('hello') + v1; --> Python exception You can write also: There are several facility functions that let you test the different types you can access the sys module with the function SysModule, or you can import You can create a Python variant with: you can access to the Python object pointer stored in the variant with you can test the variant with: you can check if 2 variants shares the same Python object with you can check if an instance has a class that is or inherits from a class or you can check the inheritence between 2 classes withL Note that these 2 functions requires Python 2 or later. You can check None with:
Note, that your class object must the property of a container and can't be
Feel free to give your comments... Morgan
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Using Delphi and Python together - An ExampleA Delphi app which has all the business logic implemented as Python code. A perfect marriage of two worlds! The Delphi Code
unit mainFrm; interface uses Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, PythonEngine, AtomPythonEngine, StdCtrls, ExtCtrls, PythonGUIInputOutput, uHeartMachine; type
TfrmMain = class(TForm)
PE: TAtomPythonEngine;
PythonInputOutput1: TPythonInputOutput;
pdvUser: TPythonDelphiVar;
pdvShare: TPythonDelphiVar;
pdvOrderManager: TPythonDelphiVar;
pdvBankBalance: TPythonDelphiVar;
pdvNumShares: TPythonDelphiVar;
pdvSharePrice: TPythonDelphiVar;
PythonDelphiVar2: TPythonDelphiVar;
lblSharePrice: TLabel;
bntBuy: TButton;
btnForceStockToDrop: TButton;
Timer1: TTimer;
lblBankBalance: TLabel;
lblNumShares: TLabel;
btnSell: TButton;
Memo1: TMemo;
Label1: TLabel;
Label2: TLabel;
Label3: TLabel;
Label4: TLabel;
lblSharesAreWorth: TLabel;
Label5: TLabel;
PythonGUIInputOutput1: TPythonGUIInputOutput;
btnForceStockToRise: TButton;
cbNumShares: TComboBox;
Label6: TLabel;
cbUserLimit: TComboBox;
Label7: TLabel;
lblTotalWorth: TLabel;
Label8: TLabel;
cbNumAttempts: TComboBox;
Label9: TLabel;
Panel1: TPanel;
HeartMachine1: THeartMachine;
Panel2: TPanel;
HeartMachine2: THeartMachine;
Panel3: TPanel;
HeartMachine3: THeartMachine;
procedure PythonInputOutput1SendData(Sender: TObject;
const Data: String);
procedure pdvSharePriceSetData(Sender: TObject; Data: Variant);
procedure FormShow(Sender: TObject);
procedure bntBuyClick(Sender: TObject);
procedure btnForceStockToDropClick(Sender: TObject);
procedure Timer1Timer(Sender: TObject);
procedure btnSellClick(Sender: TObject);
procedure btnForceStockToRiseClick(Sender: TObject);
procedure cbUserLimitChange(Sender: TObject);
procedure cbNumAttemptsChange(Sender: TObject);
procedure PEPathInitialization(Sender: TObject; var Path: String);
private
{ Private declarations }
public
{ Public declarations }
end;
TmgmStockMarketMainForm = class(TObject) // ; // Transformation Interface
private
LastPrice : integer;
public
procedure display;
procedure repopulateFromGui;
end;
var frmMain: TfrmMain; implementation uses AndyDelphiPy, ComCtrls, pythonAtom, Math; var Share, User, OrderManager : OleVariant; mgmMainForm : TmgmStockMarketMainForm; {$R *.DFM}
procedure TfrmMain.PythonInputOutput1SendData(Sender: TObject; const Data: String); begin PyConsoleOut(Data); end; procedure TfrmMain.pdvSharePriceSetData(Sender: TObject; Data: Variant); begin lblSharePrice.Caption := Data; end; procedure TfrmMain.FormShow(Sender: TObject);
begin
//PyExeFile('E:\Python20\Boa-0.0.5\AndysTry\Questtest.py', PE);
PyExeFile('QuesttestFROZEN.py', PE);
User := PyClass('User()', pdvUser, PE);
Share := PyClass('Share("Friendly Co.", worth=10)', pdvShare, PE);
OrderManager := PyClass('OrderManager()', pdvOrderManager, PE);
mgmMainForm := TmgmStockMarketMainForm.Create;
timer1.enabled := true;
end;
procedure TfrmMain.bntBuyClick(Sender: TObject); begin OrderManager.AddOrder(User.myself, strtoint(cbNumShares.text), 'buy', Share.myself); end; procedure TfrmMain.btnSellClick(Sender: TObject); begin OrderManager.AddOrder(User.myself, strtoint(cbNumShares.text), 'sell', Share.myself); end; procedure TfrmMain.Timer1Timer(Sender: TObject);
begin
try
Share.fluxtuate;
OrderManager.ProcessOrders;
mgmMainForm.display;
except
timer1.enabled := false;
showmessage('Some error cancelled the game.');
end;
end;
{ TmgmStockMarketMainForm }
procedure TmgmStockMarketMainForm.display;
var
f : double;
begin
if LastPrice = Share.CurrentPrice then
with frmMain.lblSharePrice do
Caption := Caption + '.'
else
frmMain.lblSharePrice.Caption := '$ ' + inttostr(Share.CurrentPrice);
LastPrice := Share.CurrentPrice;
f := User.BankBalance;
frmMain.lblBankBalance.Caption := format('%m', [ f ]);
frmMain.lblNumShares.Caption := User.NumSharesOwned;
f := User.NumSharesOwned * Share.CurrentPrice;
frmMain.lblSharesAreWorth.Caption := format('%m', [ f ]);
f := f + User.BankBalance;
frmMain.lblTotalWorth.Caption := format('%m', [ f ]);
frmMain.cbNumAttempts.Text := OrderManager.MaxAttempts; frmMain.cbUserLimit.Text := User.SharePriceLimit; frmMain.HeartMachine1.AddPoint(0, min(Share.CurrentPrice, 100), 'Share Price'); frmMain.HeartMachine2.AddPoint(0, min(User.BankBalance, 50000), 'Bank Balance'); frmMain.HeartMachine3.AddPoint(0, min(User.NumSharesOwned, 1000), 'Num Shares Owned'); end; procedure TmgmStockMarketMainForm.repopulateFromGui; begin User.SharePriceLimit := strtoint( frmMain.cbUserLimit.Text ); OrderManager.MaxAttempts := strtoint( frmMain.cbNumAttempts.Text ); display; end; procedure TfrmMain.cbUserLimitChange(Sender: TObject); begin mgmMainForm.repopulateFromGui; end; procedure TfrmMain.cbNumAttemptsChange(Sender: TObject); begin mgmMainForm.repopulateFromGui; end; procedure TfrmMain.btnForceStockToRiseClick(Sender: TObject); begin Share.CurrentPrice := Share.CurrentPrice + 10 + random(20); end; procedure TfrmMain.btnForceStockToDropClick(Sender: TObject); begin Share.CurrentPrice := random(10); end; procedure TfrmMain.PEPathInitialization(Sender: TObject; var Path: String); begin //path := 'e:\try\deploy;e:\try\deploy\lib'; end; end.
The Python CodeNote: Not all the python code is shown, due to confidentiality issues. # Share trading game simulator. false = 0 ; true = 1 import random, sys def log(s):
print s
#sys.stdout.flush()
class Share:
def __init__(self, name, worth=10):
self.CurrentPrice = worth
self.Name = name
def __str__(self):
return 'Share ' + self.Name + ' Worth= $' + `self.CurrentPrice` + ' per share.'
def fluxtuate(self):
if random.randrange(0,2):
self.CurrentPrice = self.CurrentPrice + random.randrange(-10,10)
if self.CurrentPrice <= 0:
self.CurrentPrice = 1
##log('..time passes.. ' + str(self))
def myself(self):
return self
class User:
def __init__(self, initialBankBalance=1000, initialNumShares=0, initialSharePriceLimit=10):
self.BankBalance = initialBankBalance
self.NumSharesOwned = initialNumShares
self.SharePriceLimit = initialSharePriceLimit
def __str__(self):
return 'User Bank balance='+`self.BankBalance` + \
' Number of Shares=' + `self.NumSharesOwned` + \
' Share Price Limit=' + `self.SharePriceLimit`
def myself(self):
return self
class Order:
def candivest(self):
return self.NumberOfShares <= self.User.NumSharesOwned
def canafford(self):
return (self.Share.CurrentPrice*self.NumberOfShares) < self.User.BankBalance
def sharepricetoolow(self):
return self.Share.CurrentPrice < self.User.SharePriceLimit
def sharepricetoohigh(self):
return self.Share.CurrentPrice > self.User.SharePriceLimit
def __init__(self, user, numshares, buyorsell, share):
self.User = user
self.Share = share
self.NumberOfShares = numshares
self.Command = buyorsell
#print 'DEBUG - self.Share.CurrentPrice', self.Share.CurrentPrice # debug !!!!
def __str__(self):
return 'Order to %s %d %s shares' % (self.Command, self.NumberOfShares, self.Share.Name)
etc. Related 'Python for Delphi' Links on this site:
return to main Andy Patterns home page |
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Related 'Python for Delphi' Links on this site:
return to main Andy Patterns home page
Deploying Python for Delphi applicationsWhen deploying delphi application that uses the python for delphi components, you need to supply python21.dll (or whatever version you are working with) plus any .py files. Simple advice, but the devil is in the detail - as I found out!! Nevertheless, I managed to successfully deploy a delphi app to hundreds of users and they didn't even know there was python inside ! -Andy Bulka Quick tipsTips:
Does the python for delphi demo25 rely on python 2.1?Andy: It seems that Demo25 does indeed rely on both delphi 6 and python 2.1 Morgan: Demo25 relies on Python2.1 indirectly, as it calls the function VarIsInstanceOf, which relies on version 2.1, but if you comment out this call (and VarIsSubclassOf), it should work without any problem! Andy: It seems that to use, say python21.dll on a system that only has the python2.0 development environment installed, one need not fully install python 2.1, all you need to do is put python21.dll into winnt\system32 or into the folder you are developing the delphi application in. Morgan: Yes, that's right! Andy: You can put the Lib folder anywhere you like, and have Delphi point to it e.g. SysModule.path.append('..blah..\Lib'). Morgan: That's a solution, but the Python Dll gets its path from the Windows registry: HKEY_LOCAL_MACHINE\Software\Python\PythonCore\2.1\PythonPath Of course, each version of Python has its own entry.
NOTE: When supplying the python classes with your delphi exe, you can put the Lib folder anywhere you like, and point to it using the python list variant SysModule.path (accessible and modifiable from Delphi). The current folder of the Delphi EXE is automatically added to the SysModule.path (by PythonEngine, I think), so you can put Strings.py or whatever in the current folder of your Delphi application, if you like, though its probably better to follow the python standards and keep this stuff in a Lib folder. The 'DllName' property of the pythonEngineAndy: Changing the DllName property of the pythonEngine doesn't seem to affect things - even if I put python15.dll in the demo25 example, things still run ok! So how do I control / verify which python dll is being used and accessed? What is the DllName property really doing, if anything? Morgan: You forgot to disable the UseLastKnownVersion property in the TPythonEngine!!! If it's true, it tries each version of Python, starting from the greatest version number, and uses what it finds. If nothing is found, then DllName is used! So, if you have several versions of Python installed in your system, you can't rely on this property, and you should set it to False and define the DllName corresponding to the expected Python version, but don't forget to specify the properties APIVersion and RegVersion. If you have a doubt, look at the beginning of PythonEngine.pas, that defines all known values in an array (PYTHON_KNOWN_VERSIONS). [ Note: You don't even need to set UseLastKnownVersion to false now, because the latest strategy is to find first the dll for which your code was compiled, and then try to upgrade if it's missing. ] Compiling for different versions of pythonRunning python 2.2 from delphi 6Andy: I am getting an error when I start my dephi app 'Error 127: could not map symbol "PyUnicode_FromWideChar" This is the first time I've tried running a python 2.2.1 app. I was using 2.1 ok, then to change to 2.2 I changed the AtomEngine component properties: Morgan: You don't need to do this for selecting a Python version! Keep UseLastKnownVersion to True, and adjust your defines: Andy: Ok it works now. :-) These two steps seem to be the key to getting it working and all I have to do. When I turn UseLastKnownVersion to false, I get into trouble I was having. Furthermore, playing with
Cleaning up my python path from within DelphiAndy Bulka I want to ship (with my .exe) a few python units in the 'MyLib' folder underneath where my delphi .EXE lives. The destination machine doesn't have python, so I need to supply all the relevant classes (by the way are there any dependency utils for ensuring I identify all the dependent class files?) Anyway, so I want to set the sys.path appropriately to make sure my python class files are found. Of course I could put all the classes in the same folder as my EXE and this would solve the problem, cos I know the current folder of my EXE is automatically added to the sys.path. But I want to keep my python classes in the 'MyLib' folder underneath where my delphi .EXE lives. I know that when a python engine starts up inside delphi, the sys.path is set via the Windows registry: If I'm using Delphi 6 and python 2.1 then I can use the following cool delphi code to trim the path and set it to something I want. SysModule.path := NewPythonList;
SysModule.path.append(ExtractFilePath( Application.ExeName ) + 'MyLib' );
SysModule.path.append('some other folder');
NOTE: Above relies on Jan 2002 version of python for Delphi components. MY QUESTION: Under delphi 4, I don't have access to the variant unit and the nice SysModule variable. Is the only alternative to send some python script text at the python interpreter to set sys.path ? e.g. Memo1.Lines.Text := 'import sys' ; PythonEngine1.ExecStrings( Memo1.Lines ); apath := ExtractFilePath( Application.ExeName ) + 'MyLib' ; Memo1.Lines.Text := 'sys.path.append("' + apath + '")' ; PythonEngine1.ExecStrings( Memo1.Lines ); **** above code works, ok by the way
Morgans' reply:You have another solution by using Python APIs: Here are some sys APIs: function PySys_GetObject(s:PChar):PPyObject; cdecl; function PySys_SetObject(s:PChar;ob:PPyObject):integer; cdecl; procedure PySys_SetPath(path:PChar); cdecl; procedure PySys_SetArgv( argc: Integer; argv: PPChar); cdecl; PySys_SetPath('c:\mylib');
it will be the same than doing in Python: import sys sys.path = 'c:\\mylib'; if you want to know the path content, simply use PySys_GetObject('path') and it will return a borrowed reference to the Python path string object. If you want to replace it, you can do: PySys_SetObject('path',MyNewPathStringObject);
But don't forget to decrement the reference count of MyNewPathStringObject. void
PySys_SetPath(char *path)
{
PyObject *v;
if ((v = makepathobject(path, DELIM)) == NULL)
Py_FatalError("can't create sys.path");
if (PySys_SetObject("path", v) != 0)
Py_FatalError("can't assign sys.path");
Py_DECREF(v);
}
Compiling delphi app to use specific versions of python dll.I've was playing with using different versions of python from delphi, using the latest release of your components. Here are some scenarios:
Note: Compiling issues. Set the DEFINE inside the project you are using. setting it in the python for delphi package options does not help since whilst the package is fine, the .exe you build uses .dcu's which are recompiled on demand, using your project options. Thus you need to set the actual project options. here is a viewlet demo of this technique. -Andy Bulka.
How to get python for Delphi to stop looking at the PYTHONPATH environment variable and at any existing python path in the registryQuestion: Do you know any way to stop python21 from If I want a truly independent distibution, then supplying my own libs and python21.dll can be thwarted by the user's machine happening to have a I tried clearing the PYTHONPATH dos environment variable in delphi, prior to creating a form on which the atomengine lived - but it seems that python is I soon intend to write an article about deploying with python for delphi, including the issues & gotchas I have encountered, so any thoughts about this cheers, P.S. Can you suggest how to avoid picking up pythonpath? I scanned through the components source code and you only look in the registry for PythonPath, so python itself must be looking at the dos environment. I have set the engine dll name manually in the property editor. I have set UseLastKnown to false, and verified the correct dll is being loaded. The python21.dll is in the same directory as the exe, and the Lib and DLLs folders underneath the folder with the exe. Even the solution of clearing this environment variable BEFORE the form/datamodule with the python engine is even created.helps in some apps, but for others doesn't work either. Initial reply from Morgan> Whilst I've got your attention - do you know any way to stop python21 from looking at PYTHONPATH environment variable, when loaded from delphi? Morgan: Not especially! > If I want a truly independent distibution, then supplying my own libs and python21.dll can be thwarted by the user's machine happening to have a PYTHONPATH defined, and pointing to an old set of python libs (e.g. python20). The wrong os.py gets loaded etc. etc. Even if the first thing I do in a Morgan: Ok. > I tried clearing the PYTHONPATH dos environment variable in delphi, prior to creating a form on which the atomengine lived - but it seems that python is loaded into a fresh process space with a fresh set of environment variables (including the nasty PYTHONPATH ). Note that sometimes this solution DID work e.g. on a simple sample app (thus looked like a promising solution) - but didn't work for my big serous delphi app - not sure why not, perhaps cos of the Morgan: Ok. Anyway, you have to clear the registry also. A Dll shares the same address space of the process it runs into. >It may apply to registry paths too, if you want to override any existing libs and supply your own. I noticed in python 22 there was something about a flag to ignore the environment - perhaps that is also relevant? Morgan: It doesn't work with Windows, only Unix. I looked at Python source code and found out a way: Simply add the following line of code in the OnBeforeLoad event of SetEnvironmentVariable('PYTHONHOME', 'c:\myHome');
And it will generate the following path: ['D:\\Users\\Morgan\\PythonForDelphi\\Demos\\Demo25', 'c:\\myHome\\DLLs', 'c:\\myHome\\lib', 'c:\\myHome\\lib\\plat-win', 'c:\\myHome\\lib\\lib-tk', 'D:\\Users\\Morgan\\PythonForDelphi\\Demos\\Demo25'] In fact, I should even add a special event for this... Here are some comments extracted from Python source code: All PC ports use this scheme to try to set up a module search path: from PC\readme.txt 1) The script location; the current directory without script. 2) The PYTHONPATH variable, if set. 3) For Win32 platforms (NT/95), paths specified in the Registry. 4) Default directories lib, lib/win, lib/test, lib/tkinter; these are searched relative to the environment variable PYTHONHOME, if set, or relative to the executable and its ancestors, if a landmark file (Lib/string.py) is found , or the current directory (not useful). 5) The directory containing the executable. from PC\getpathp.c /* We need to construct a path from the following parts. (1) the PYTHONPATH environment variable, if set; (2) for Win32, the machinepath and userpath, if set; (3) the PYTHONPATH config macro, with the leading "." of each component replaced with pythonhome, if set; (4) the directory containing the executable (argv0_path). The length calculation calculates #3 first. Extra rules: - If PYTHONHOME is set (in any way) item (2) is ignored. - If registry values are used, (3) and (4) are ignored. */ Afterthought....From: Morgan Martinet [morgan.martinet@altavista.net] Hi again! In my last mail I omitted a point: I had removed the registry entries of Python, and it worked fine. But have proper registry settings override the PYTHONHOME path, as they are placed first in the path list. Anyway, I discovered that you can define your own Python settings in the current user registry, and they will override the default settings of local machine! So, with regedit I defined the following entries: Windows Registry Editor Version 5.00 [HKEY_CURRENT_USER\Software\Python] [HKEY_CURRENT_USER\Software\Python\PythonCore] [HKEY_CURRENT_USER\Software\Python\PythonCore\2.1] [HKEY_CURRENT_USER\Software\Python\PythonCore\2.1\PythonPath] @="d:\\default" [HKEY_CURRENT_USER\Software\Python\PythonCore\2.1\PythonPath\PythonWin] @="d:\\pythonwin" [HKEY_CURRENT_USER\Software\Python\PythonCore\2.1\PythonPath\Win32] @="d:\\win32com" [HKEY_CURRENT_USER\Software\Python\PythonCore\2.1\PythonPath\win32com] And I get the following path from Python: ['D:\\Users\\Morgan\\PythonForDelphi\\Demos\\Demo25', 'd:\\pythonwin', 'd:\\win32com', 'D:\\Users\\Morgan\\PythonForDelphi\\Demos\\Demo25', 'd:\\default', 'C:\\Python21\\Pythonwin', 'C:\\Python21\\win32', 'C:\\Python21\\win32\\lib', 'C:\\Python21', 'C:\\Python21\\Lib\\plat-win', 'C:\\Python21\\Lib', 'C:\\Python21\\DLLs', 'C:\\Python21\\Lib\\lib-tk'] Hope this helps, Andy still is not clear:So you are saying that inserting d:\\default into PythonPath is also needed? in conjunction with SetEnvironmentVariable('PYTHONHOME', 'd:\default'); So in summary, the combination: SetEnvironmentVariable('PYTHONHOME', 'c:\myHome');
and [HKEY_CURRENT_USER\Software\Python\PythonCore\2.1\PythonPath]@="d:\\default"
( the latter hopefully should appear before any other refs to any other \lib.) will fix the problem? I'll play around some more with the new PYTHONHOME idea. But try point your PYTHONPATH to a python20 lib folder and load python21.dll via delphi, and load os and urllib etc. Weird things happen unless the correct versions are loaded, that's for sure. I'll see how the PYTHONHOME works... Morgan's final word on this issue:You don't even need to use: SetEnvironmentVariable('PYTHONHOME', 'c:\myHome'); Simply override the Python registry settings for the current user, as you can't do it for the local machine if the logged user has not admin rights. Andy's final Solution:I never did resolve this. So I just added some code to the delphi app which checked to see if PYTHONPATH was defined. If it was, the app refuses to run. I just couldn't afford to take chances and didn't have the time to resolve this issue to my satisfaction. Anybody else is welcome to email me so I can do a final summary.
Where does python for delphi look for the DLL at run time?>Is there any way I can control WHERE it looks for the DLL at run time? Yes, simply set the property UseLastKnownVersion to False, and set the property DllName to the fully qualified path of your python21.dll. Don't forget to set the properties APIVersion to 1010 and RegVersion to 2.1 If you want to do it by code, you must also set the property AutoLoad to False, and set the previous properties in the OnCreate event of your form or datamodule, and finally call the method LoadDll. Note that in the next release, I will add a property to specify the Dll's folder. Hope this helps, Morgan
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