Python字典部分源码分析，字典是无序的

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

#练习1、清空字典（置空）
li = {"key1":"value1","key2":"value2"}
li.clear()     #清空所有
print(li)
#执行结果：
{}

def copy(self): # real signature unknown; restored from __doc__
        """ D.copy() -> a shallow copy of D """
        pass

#练习2、浅拷贝
li = {"key1":"value1","key2":"value2","key3":"value3"}
dd = li.copy()    #浅拷贝
print(li)
print(dd)
#执行结果：
{'key2': 'value2', 'key3': 'value3', 'key1': 'value1'}
{'key2': 'value2', 'key3': 'value3', 'key1': 'value1'}

 @staticmethod # known case
    def fromkeys(*args, **kwargs): # real signature unknown
        """ Returns a new dict with keys from iterable and values equal to value. """
        pass

#练习3、迭代字符串生成同一值，放到新字典
li = {"key1":"value1","key2":"value2","key3":"value3"}
xin = li.fromkeys("key1","444")
print(xin)
aa = li.fromkeys("ttb","value1")  #分别迭代字符串生成同一个值，放在新字典中，与原字典好像没什么关系
print(aa)
#执行结果：
{'1': '444', 'y': '444', 'e': '444', 'k': '444'}
{'b': 'value1', 't': 'value1'}

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. """
        pass

#练习4、获取指定键的值
li = {"key1":"value1","key2":"value2","key3":"value3"}
aa = li.get("key2")    #获取指定键的值
print(aa)
#执行结果
value2

def items(self): # real signature unknown; restored from __doc__
        """ D.items() -> a set-like object providing a view on D's items """
        pass

#练习5、获取字典所有内容
li = {"key1":"value1","key2":"value2","key3":"value3"}
aa = li.items()    #获取字典所有
print(aa)
#执行结果：
dict_items([('key1', 'value1'), ('key3', 'value3'), ('key2', 'value2')])

def keys(self): # real signature unknown; restored from __doc__
        """ D.keys() -> a set-like object providing a view on D's keys """
        pass

练习6、获取字典中所有键
li = {"key1":"value1","key2":"value2","key3":"value3"}
aa = li.keys()    #获取字典所有键
print(aa)
#执行结果：
dict_keys(['key2', 'key3', 'key1'])

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
        """
        pass

#练习7、删除指定键
li = {"key1":"value1","key2":"value2","key3":"value3"}
aa = li.pop("key2")    #删除指定键，连带删除值
print(li)
#执行结果
{'key1': 'value1', 'key3': 'value3'}

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.
        """
        pass

#练习8、随机删除键值
li = {"key1":"value1","key2":"value2","key3":"value3"}
aa = li.popitem()    #随机删除指定键，连带删除值
print(li)
#执行结果：（）随机删掉一个
{'key3': 'value3', 'key1': 'value1'}

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 """
        pass

#练习9、输出指定键值，键不存在则加入字典
li = {"key1": "value1", "key2": "value2", "key3": "value3"}
aa = li.setdefault("key1","111")  # 键存在字典中时，相当于li.get("key1"),不管后面加什么都没影响
print(aa)
bb = li.setdefault("kkk","111")   #键不存在时，输入值，并且该键值会加入到字典中
print(bb)
print(li)
执行结果：
value1
111
{'key2': 'value2', 'key1': 'value1', 'kkk': '111', 'key3': 'value3'}

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

#练习10、更新字典
li = {"key1": "value1", "key2": "value2", "key3": "value3"}
aa = {"key1":"111","key2":"222"}
li.update(aa)      #aa是新的，把新的放进旧的，如果键相同则改变值，如果键不同则直接加入
print(li)
li1 = {"key1": "value1", "key2": "value2", "key3": "value3"}
aa1 = {"key1":"111","key2":"222"}
aa1.update(li1)
print(aa1)
#执行结果：
{'key3': 'value3', 'key1': '111', 'key2': '222'}
{'key3': 'value3', 'key1': 'value1', 'key2': 'value2'}

def values(self): # real signature unknown; restored from __doc__
        """ D.values() -> an object providing a view on D's values """
        pass

#练习11、输出字典所有值
li = {"key1": "value1", "key2": "value2", "key3": "value3"}
aa = li.values()    #输出字典所有的值
print(aa)
执行结果：
dict_values(['value3', 'value2', 'value1'])