dict文档

文档

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class dict(object):     """     dict() -> new empty dictionary     创建字典的方式有两种：     1、dic = {}     2、dic = dict()     ----------------------------------------------------------------------     dict(mapping) -> new dictionary initialized from a mapping object's         (key, value) pairs     dict(iterable) -> new dictionary initialized as if via:         d = {}         for k, v in iterable:             d[k] = v     dict(**kwargs) -> new dictionary initialized with the name=value pairs         in the keyword argument list.  For example:  dict(one=1, two=2)     """     def clear(self): # real signature unknown; restored from __doc__         """         D.clear() -> None.  Remove all items from D.         清空字典         """         pass       def copy(self): # real signature unknown; restored from __doc__         """         D.copy() -> a shallow copy of D         拷贝一个字典         跟列表的lcopy方法类似，也是一个浅拷贝，如果字典里面嵌套字典或者列表，内层不会         如果需要深拷贝，也要导入copy模块         --------------------------------------------------------------------------         dic3 = {'k1':{'kk1':1},'k2':{'kk2':'2'}}         dic4 = dic3.copy()         print(dic3['k1'] is dic4['k1'])    # True         dic3['k1']['kk1'] = 'kkk1'         print(dic3)         print(dic4)         """         pass       @staticmethod # known case     def fromkeys(*args, **kwargs): # real signature unknown         """         Returns a new dict with keys from iterable and values equal to value.         创建一个新的字典，字典的key是从第一个参数（可迭代对象）里一一获取的，         value值是从第二个参数（任意数据类型），默认是None         注意！这个是一个静态方法，是用dict类直接调用的！！！         ---------------------------------------------------------------------------         s = 'fuyong'         d1 = dict.fromkeys(s)         print(d1)          # {'g': None, 'n': None, 'f': None, 'y': None, 'u': None, 'o': None}           l = ['a','b','c']         d2 = dict.fromkeys(l,1000)         print(d2)         # {'a': 1000, 'b': 1000, 'c': 1000}         ----------------------------------------------------------------------------          """         pass       def get(self, k, d=None): # real signature unknown; restored from __doc__         """         D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None.         根据key值来查找value值         如果找不到不会报错，返回None         -------------------------------------------------------------------------------         d1 = {'a':'b'}         print(d1.get('a'))      # b         print(d1.get('c'))      # None         """         pass       def items(self): # real signature unknown; restored from __doc__         """         D.items() -> a set-like object providing a view on D's items         将字典的每一个元素的key和value值放到一个元组里，然后以一个类似列表形式包起来         但是返回值不是一个列表,而是一个dict_items对象         ---------------------------------------------------------------         d1 = {'a':1,'b':2}         print(d1.items())           # dict_items([('b', 2), ('a', 1)])         print(type(d1.items()))     # <class 'dict_items'>         ----------------------------------------------------------------         可以用循环的方式遍历items         for k,v in d1.items():             print(k,v)         # b 2         # a 1         """         pass       def keys(self): # real signature unknown; restored from __doc__         """         D.keys() -> a set-like object providing a view on D's keys         获取字典所有key，以一个类似于列表的东西包起来，是一个dict_keys对象         可以遍历所有value         ------------------------------------------------------------------------         d1 = {'a':1,'b':2}         print(d1.keys())            # dict_keys(['a', 'b'])         print(type(d1.keys()))      # <class 'dict_keys'>         """         pass       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, d is returned if given, otherwise KeyError is raised         按照指定的key删除一个字典中的元素         如果能找到key值，则会返回删除元素的值         如果找不到指定的key，会报错         ---------------------------------------------------------------------------         d1 = {'a':1,'b':2,'c':3}         print(d1.pop('a'))         """         pass       def popitem(self): # real signature unknown; restored from __doc__         """         D.popitem() -> (k, v), remove and return some (key, value) pair as a         2-tuple; but raise KeyError if D is empty.         随机删除一个字典里的元素，并且以元组的形式将被删除的键值对返回         如果字典为空则会报错         -------------------------------------------------------------------------         d1 = {'a':1,'b':2,'c':3}         print(d1.popitem())         # 因为是随机删除，每次执行返回值不同         """         pass       def setdefault(self, k, d=None): # real signature unknown; restored from __doc__         """         D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D         1、如果key值在原字典里存在：         不会被改变         d1 = {'a':1,'b':2,'c':3}         d1.setdefault('b')         print(d1)                   # {'a': 1, 'b': 2, 'c': 3}         d1.setdefault('b',222)      # {'a': 1, 'b': 2, 'c': 3}         print(d1)         -----------------------------------------------------------------------------------         2、如果key值在原字典里不存在：         会在字典里添加一个键值对，如果不指定value值，则设置为None         d1 = {'a':1,'b':2,'c':3}         d1.setdefault('d')         print(d1)                   # {'a': 1, 'c': 3, 'd': None, 'b': 2}         d1.setdefault('e',6)         # print(d1)                 # {'a': 1, 'c': 3, 'e': 6, 'd': None, 'b': 2}         """         pass       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]         更新一个字典，可以将另一个字典添加进去         ----------------------------------------------------------------------------         d1 = {'a':1,'b':2,'c':3}         d2 = {'d':4,'e':5}         d1.update(d2)         print(d1)               # {'c': 3, 'a': 1, 'b': 2, 'e': 5, 'd': 4}         """         pass       def values(self): # real signature unknown; restored from __doc__         """         D.values() -> an object providing a view on D's values         获取字典所有value，以一个类似于列表的东西包起来，是一个dict_values对象         可以遍历所有value         -------------------------------------------------------------------------------         d1 = {'a':1,'b':2}         print(d1.values())              # dict_values([2, 1])         print(type(d1.values()))        # <class 'dict_values'>           """         pass

示例

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dic1 = {} dic2 = dict() print(type(dic1),type(dic2))   dic3 = {'k1':{'kk1':1},'k2':{'kk2':'2'}} dic4 = dic3.copy()   print(dic3['k1'] is dic4['k1'])    # True   dic3['k1']['kk1'] = 'kkk1' print(dic3) print(dic4)   s = 'fuyong' d1 = dict.fromkeys(s) print(d1)   l = ['a','b','c'] d2 = dict.fromkeys(l,1000) print(d2)   d1 = {'a':'1,b':2} print(d1.get('a')) print(d1.get('c'))   d1 = {'a':1,'b':2} print(d1.items()) print(type(d1.items()))   for k,v in d1.items():     print(k,v)   d1 = {'a':1,'b':2} print(d1.keys()) print(type(d1.keys()))     d1 = {'a':1,'b':2} print(d1.values()) print(type(d1.values()))     d1 = {'a':1,'b':2,'c':3} print(d1.pop('a'))   d1 = {'a':1,'b':2,'c':3} print(d1.popitem())   d1 = {'a':1,'b':2,'c':3} d1.setdefault('b') print(d1) d1.setdefault('b',222) print(d1)   d1 = {'a':1,'b':2,'c':3} d1.setdefault('d') print(d1) d1.setdefault('e',6) print(d1)     d1 = {'a':1,'b':2,'c':3} d2 = {'d':4,'e':5} d1.update(d2) print(d1)