python-05

去除空格

方法一：使用字符串

#!/usr/bin/env python 
whitespace = ' \t\n\r\v\f'
def myStrip(chs):
    pass
def myLstrip(chs):
    if len(chs) ==0:
        return chs
    strlen = len(chs)
    for i in range(strlen):
        if chs[i] not in whitespace:
            break
    else:
        return ''
    return chs[i:]
def myRstrip(chs):
    if len(chs) == 0:
        return chs
    strlen =len(chs)
    for i in range(-1, -(strlen + 1), -1):
        if chs[i] not in whitespace:
            break
    else:
        return ''
    return chs[:i + 1]
if __name__ == '__main__':
    myStr = '  hello    '
    print '|' + myStr + '|'
#    print '|' + myStrip[myStr] + '|'
    print '|' + myLstrip(myStr) + '|'
    print '|' + myRstrip(myStr) + '|'

方法二：使用列表

#!/usr/bin/env python 
whitespace = ' \t\n\r\v\f'
def myStrip(chs):
    pass
def myLstrip(chs):
    if len(chs) == 0:
        return chs
    chsList = []
    chsList.extend(chs)
    for i in range(len(chsList)):
        if chsList[0] in whitespace:
            chsList.pop(0)
        else:
            break
    return ''.join(chsList)
def myRstrip(chs):
    if len(chs) == 0:
        return chs
    chsList = []
    chsList.extend(chs)
    for i in range(len(chsList)):
        if chsList[-1] in whitespace:
            chsList.pop()
        else:
            break
    return ''.join(chsList)
if __name__ == '__main__':
    myStr = '  hello    '
    print '|' + myStr + '|'
#    print '|' + myStrip[myStr] + '|'
    print '|' + myLstrip(myStr) + '|'
    print '|' + myRstrip(myStr) + '|'

创建一个整数到IP地址的转换程序，如下格式：WWW.XXX.YYY.ZZZ

如2130706433转换为127.0.0.1

#!/usr/bin/env python
def ip2int(ipaddr):
    iplist = ipaddr.split('.')
    result = 0
    for i in range(4):
        result += int(iplist[i]) * (256 ** (3 - i))
    return result
def int2ip(num):
    iplist = []
    for i in range(3):
        num, modnum = divmod(num, 256)
        iplist.insert(0,str(modnum))
    iplist.insert(0, str(num))
    return '.'.join(iplist)
def test():
    ip = raw_input('Input an ip address: ')
    print ip2int(ip)
    number = int(raw_input('Input a number: '))
    print int2ip(number)
if __name__ == '__main__':
    test()

一、字典的定义

>>> mydict = {'name' : 'tom', 'age' : 23}
>>> adict = {}
>>> bdict = {}.fromkeys(('x', 'y'), 10)
>>> bdict
{'y': 10, 'x': 10}
打印字典的每个键－值对：
>>> for eachKey in bdict:
...     print '%s:%s' % (eachKey,bdict[eachKey])
... 
y:10
x:10
>>> bdict
{'y': 10, 'x': 10}
更新字典
>>> mydict['name'] = bob
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'bob' is not defined
>>> mydict['name'] = 'bob'
>>> mydict['email'] = 'bob@test.com'
>>> mydict
{'age': 23, 'name': 'bob', 'email': 'bob@test.com'}、
删除
>>> del mydict['age']
>>> 
>>> mydict
{'name': 'bob', 'email': 'bob@test.com'}
>>> mydict.pop('name')
'bob'
>>> mydict
{'email': 'bob@test.com'}
>>> mydict.clear()
>>> mydict
{}

二、字典的方法：

>>> mydict = {'name' : 'bob', 'age' : 23}
>>> mydict
{'age': 23, 'name': 'bob'}
>>> mydict.keys()        返回键
['age', 'name']
>>> mydict.values()        返回值
[23, 'bob']
>>> mydict.items()        返回键－值对的元组列表
[('age', 23), ('name', 'bob')]
>>> adict = {'email' : 'tom@test.com', 'phone' : '123456'}
>>> mydict.update(adict)        把adict的内容，加入到mydict中
>>> mydict
{'phone': '123456', 'age': 23, 'name': 'bob', 'email': 'tom@test.com'}
>>> adict
{'phone': '123456', 'email': 'tom@test.com'}

三、字典练习

#!/usr/bin/env python
import getpass
db = {}
def newUser():
    username = raw_input('username: ')
    if username in db:
        print "\033[32;1m%s alread exist!\033[0m" % username
    else:
#        password = raw_input('password: ')
        password = getpass.getpass()
        db[username] = password
def oldUser():
    username = raw_input('username: ')
    password = raw_input('password: ')
    if username in db:
        if db.get(username) == password:
            print '\033[32;1mlogin successful1\033[0m'
        else:
            print '\033[32;1mlogin incorrect.\033[0m'
    else:
        print '\033[32;1mlogin name is error.\033[0m'
CMDs = {'n' : newUser, 'o' : oldUser}
def showMenu():
    prompt = '''(New) user
(Old) user
(Quit).
please input your choice: '''
    while True:
        choice = raw_input(prompt).strip()[0].lower()
        if choice not in 'noq':
            print '\033[31;1merror : n/o/q ...\033[0m'
            continue
        if choice == 'q':
            break
        CMDs[choice]()
if __name__ == '__main__':
    showMenu()

一、条件及语句

1、在python中没有case语句，可以使用if/elif,或者使用字典

#!/usr/bin/env python
db = { 'create' : 'aaaa', 'del' : 'bbbb', 'modify' : 'cccc'}
choice = raw_input('enter something:')
if db.get(choice):
    print db[choice]

2、使用元组代替case

#!/usr/bin/env python
choice = raw_input('enter something:')
if choice in ('create', 'delete', 'update'):
    action = '%s item' % choice
    print action

3、三元运算符

>>> x = 8
>>> y = 5
>>> smaller = x if x < y else y
>>> smaller
5

迭代器

>>> i = iter(range(10))
>>> for j in i:
...     print j
... 
0
1
2
3
4
5
6
7
8
9
>>> i = iter(range(4))
>>> i.next()
0
>>> i.next()
1
>>> i.next()
2
>>> i.next()
3
>>> i.next()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
>>> a = xrange(3)
>>> print a
xrange(3)
>>> for i in a:
...     print i
... 
0
1
2

4、使用range计算阶乘

#!/usr/bin/env python
a = 1
num = int(raw_input('enter a number:'))
for i in range(1, num + 1):
   a *= i
print a

5、使用递归函数计算阶乘

#!/usr/bin/env python
def cf(num):
    if num == 1:
        return 1
    else:
        return num * cf(num - 1)
if __name__ == '__main__':
    print cf(5)

注意：

重要：

当一个日志文件很大，比如G单位，不要直接打开

f = file('new.log')

data = ( line for line in f)

data 

data.next()

文件操作

1、以只读方式打开文件

f = file('/root/bin/pwd.py')
a = f.read()    将文件的全部内容读出来，成为一个大字符串，赋值给a
f.seek(0)        将文件指针移回到文件头部
b = f.readlinse()        将文件的全部内容读出来，成为一个列表，赋值给b
f.seek(0)   将文件指针称回到文件头部
c = f.readline()   读取文件和一行，赋值给c
f.seek(0， 0) 将文件指针称回到文件头部 第一个0为偏移量 第二个0相对位置   第二个值有0/1/2   0表示文件的开头 1表示当前位置 2表示文件结尾
f.tell()   查看当前指针在什么位置
for i in f:
    print i,            因为第一行发问已经有驾车了，就不要让print再打印

练习：

读取一个文件，移除以#开头的行，将其打印在屏幕上

方法一：

#!/usr/bin/env python
import sys
def grep1(fname):
    f = file(fname)
    for i in f:
        if i != '\n' and i.strip()[0] != '#':
            print i,
    f.close()
if __name__ == '__main__':
    grep1(sys.argv[1])

方法二：

#!/usr/bin/env python
import sys
def grep1(fname):
    f = file(fname)
    for i in f:
        if i[0] in '#\n':
            continue
        else:
            print i,
    f.close()
if __name__ == '__main__':
    grep1(sys.argv[1])

方法三：推荐

#!/usr/bin/env python
import sys
try:
    f = open(sys.argv[1])
except IndexError:
    print 'you must input a filename'
except IOError:
    print 'no such file or file is a directory.'
else:
    for i in f:
        if (not i.startswith('#')) and i != '\n':
            print i,
    f.close()

方法四：

#!/usr/bin/env python
import sys
import os
def grep1(fname):
    f = open(fname)
    for i in f:
        if(not i.startswith('#')) and  i != '\n':
             print i,
    f.close()
if __name__ == '__main__':
    grep1(sys.argv[1])

来自为知笔记(Wiz)