python之字典常用语法

1. 创建字典

描述：生成字典

语法：

dic={'k1':'v1'}

样例：

dic=dict(k1='v1',k2='v2')

dic={'k1':'v1','k2':'v2'}

2. 取键值get

描述：取键值，若字典中没有键，则输出自定义字段，默认为none

语法：

    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

样例：

dic={'k1':'v1','k2':'v2'}
a=dic.get('k1')
v1
c=dic.get('k3')
none    #字典中无该键，显示none
c=dic.get('k3','no')
no   #字典中无该键，显示no

3. 取键的值

描述：取字典中的键

语法：

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

样例：

dic=dict(k1='v1',k2='v2')
dic.keys()
for k in dic.keys():
    print(k)

result：k1, k2  #显示结果

　　

4. 取键值

描述：取字典中的键值

语法：

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

样例：

dic=dict(k1='v1',k2='v2')
for v in dic.values():
    print(v)

v=v1,v2 #结果

5. 取键值对的值　　

描述：取字典中的键值对

语法：

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

样例：

dic={'k1':'v1','k2':'v2'}

for k,v in dic.items():
    print(k,v)

#结果
k1 v1
k2 v2   

6. 删除键值对　　

描述：删除字典中的键

语法：

 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

样例：

dic=dict(k1='v1',k2='v2',k3='v3')
dic.pop('k2')
print(dic)

dic={'k3': 'v3', 'k1': 'v1'}  #结果

7. 更新键值对　　

描述：更新字典中的键

语法：

   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

样例：

dic=dict(k1='v1',k2='v2',k3='v3')
dic.update({'k4':'v4'})
print(dic)

dic={'k4': 'v4', 'k3': 'v3', 'k1': 'v1', 'k2': 'v2'} #结果

8. 更新键值　　

描述：更新字典中的键

语法：

dict[key]=value　　

样例：

dic=dict(k1='v1',k2='v2',k3='v3')
dic['k1']=1
print(dic)

dic={'k3': 'v3', 'k1': 1, 'k2': 'v2'}  #结果