Python字典部分源码分析，字典是无序的

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

1 #练习1、清空字典（置空）
2 li = {"key1":"value1","key2":"value2"}
3 li.clear()     #清空所有
4 print(li)
5 #执行结果：
6 {}

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

1 #练习2、浅拷贝
2 li = {"key1":"value1","key2":"value2","key3":"value3"}
3 dd = li.copy()    #浅拷贝
4 print(li)
5 print(dd)
6 #执行结果：
7 {‘key2‘: ‘value2‘, ‘key3‘: ‘value3‘, ‘key1‘: ‘value1‘}
8 {‘key2‘: ‘value2‘, ‘key3‘: ‘value3‘, ‘key1‘: ‘value1‘}

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

1 #练习3、迭代字符串生成同一值，放到新字典
2 li = {"key1":"value1","key2":"value2","key3":"value3"}
3 xin = li.fromkeys("key1","444")
4 print(xin)
5 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
6 print(aa)
7 #执行结果：
8 {‘1‘: ‘444‘, ‘y‘: ‘444‘, ‘e‘: ‘444‘, ‘k‘: ‘444‘}
9 {‘b‘: ‘value1‘, ‘t‘: ‘value1‘}

1 def get(self, k, d=None): # real signature unknown; restored from __doc__
2         """ D.get(k[,d]) -> D[k] if k in D, else d.  d defaults to None. """
3         pass

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

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

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

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

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

1 def pop(self, k, d=None): # real signature unknown; restored from __doc__
2         """
3         D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
4         If key is not found, d is returned if given, otherwise KeyError is raised
5         """
6         pass

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

1 def popitem(self): # real signature unknown; restored from __doc__
2         """
3         D.popitem() -> (k, v), remove and return some (key, value) pair as a
4         2-tuple; but raise KeyError if D is empty.
5         """
6         pass

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

1 def setdefault(self, k, d=None): # real signature unknown; restored from __doc__
2         """ D.setdefault(k[,d]) -> D.get(k,d), also set D[k]=d if k not in D """
3         pass

 1 #练习9、输出指定键值，键不存在则加入字典
 2 li = {"key1": "value1", "key2": "value2", "key3": "value3"}
 3 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
 4 print(aa)
 5 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
 6 print(bb)
 7 print(li)
 8 执行结果：
 9 value1
10 111
11 {‘key2‘: ‘value2‘, ‘key1‘: ‘value1‘, ‘kkk‘: ‘111‘, ‘key3‘: ‘value3‘}

1 def update(self, E=None, **F): # known special case of dict.update
2         """
3         D.update([E, ]**F) -> None.  Update D from dict/iterable E and F.
4         If E is present and has a .keys() method, then does:  for k in E: D[k] = E[k]
5         If E is present and lacks a .keys() method, then does:  for k, v in E: D[k] = v
6         In either case, this is followed by: for k in F:  D[k] = F[k]
7         """
8         pass

 1 #练习10、更新字典
 2 li = {"key1": "value1", "key2": "value2", "key3": "value3"}
 3 aa = {"key1":"111","key2":"222"}
 4 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
 5 print(li)
 6 li1 = {"key1": "value1", "key2": "value2", "key3": "value3"}
 7 aa1 = {"key1":"111","key2":"222"}
 8 aa1.update(li1)
 9 print(aa1)
10 #执行结果：
11 {‘key3‘: ‘value3‘, ‘key1‘: ‘111‘, ‘key2‘: ‘222‘}
12 {‘key3‘: ‘value3‘, ‘key1‘: ‘value1‘, ‘key2‘: ‘value2‘}

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

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