python之字典

字典详解                                                    

1.clear

def clear(self): # real signature unknown; restored from __doc__
    """ D.clear() -> None.  Remove all items from D. """
    pass
翻译：删除字典元素

#!/usr/bin/python
test={'name':'test','age':22}
test.clear()
print(test)

2.copy

def copy(self): # real signature unknown; restored from __doc__
    """ D.copy() -> a shallow copy of D """
    pass
翻译：复制一份影子副本（就是第一层复制，第二层只是复制一个对象地址）

#!/usr/bin/python
test={'name':'test','age':22}
x=test.copy()
test['name']='小李'
print(test)
print(x)
test['name']={'sales':['小张','小李']}
print(test)
x=test.copy()
test['name']['sales']=['小张','小李','小王']
print(test)
print(x)

3.fromkeys

def fromkeys(*args, **kwargs): # real signature unknown
    """ Create a new dictionary with keys from iterable and values set to value. """
    pass
翻译：用可迭代对象创建一个新的字典

#!/usr/bin/python
test={'name':'test','age':22}
x=test.fromkeys([1,2,3],['a','b','c'])
print(x)

4.get

def get(self, *args, **kwargs): # real signature unknown
    """ Return the value for key if key is in the dictionary, else default. """
    pass
翻译：如果key在字典里面则返回key的值，否则默认

#!/usr/bin/python
test={'name':'test','age':22}
x=test.get('name')
print(x)

5.items

def items(self): # real signature unknown; restored from __doc__
    """ D.items() -> a set-like object providing a view on D's items """
    pass翻译：提供一个类似集合的对象，提供关于字典的项的视图

#!/usr/bin/python
test={'name':'test','age':22}
print(test.items())

6.key

def keys(self): # real signature unknown; restored from __doc__
    """ D.keys() -> a set-like object providing a view on D's keys """
    pass
翻译：提供一个类似集合的对象，提供关于字典的KEY的视图

#!/usr/bin/python
test={'name':'test','age':22}
print(test.keys())

7.values

def values(self): # real signature unknown; restored from __doc__
    """ D.values() -> an object providing a view on D's values """
    pass
翻译：提供一个类似集合的对象，提供关于字典的值的视图

#!/usr/bin/python
test={'name':'test','age':22}
print(test.values())

8.pop

def pop(self, k, d=None): # real signature unknown; restored from __doc__
    """
    D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
    
    If key is not found, default is returned if given, otherwise KeyError is raised
    """
    pass
翻译：删除key及对应的值，如果key没有找到，则报KeyError 

#!/usr/bin/python
test={'name':'test','age':22}
test.pop('name')
print(test)

9.popitem

def popitem(self, *args, **kwargs): # real signature unknown
    """
    Remove and return a (key, value) pair as a 2-tuple.
    
    Pairs are returned in LIFO (last-in, first-out) order.
    Raises KeyError if the dict is empty.
    """
    pass
翻译：删除并返回一个键值对作为二元组
对按后进先出的顺序，如果字典为空则返回KeyError

#!/usr/bin/python
test={'name':'test','age':22}
test.popitem()
print(test)

10.setdefault

def setdefault(self, *args, **kwargs): # real signature unknown
    """
    Insert key with a value of default if key is not in the dictionary.
    
    Return the value for key if key is in the dictionary, else default.
    """
    pass
翻译：如果key不在字典里面，则插入一个key并且带默认值，如果key在字典里面则返回原来值，其他默认

#!/usr/bin/python
test={'name':'test','age':22}
test.setdefault(1)
print(test)
test.setdefault(1,'default')
print(test)

11.update

def update(self, E=None, **F): # known special case of dict.update
    """
    D.update([E, ]**F) -> None.  Update D from dict/iterable E and F.
    If E is present and has a .keys() method, then does:  for k in E: D[k] = E[k]
    If E is present and lacks a .keys() method, then does:  for k, v in E: D[k] = v
    In either case, this is followed by: for k in F:  D[k] = F[k]
    """
    pass
翻译：执行更新操作，从字典对象E和F更新D
如果E存在，并且是.key(）方法，则循环更新
如果E存在，并且缺少.key()方法，则插入
其他情况，直接替换

#!/usr/bin/python
test={'name':'test','age':22}
test.update({'name':'xiaozhang'})
print(test)
test.update({'name':'xiaozhang','age':32,'sex':'男'})
print(test)