# -*- coding: utf-8 -*-
#python 27
#xiaodeng
#对UserDict的研究 class UserDict():
def __init__(self, dict=None, **kwargs):
self.data = {} #定义self.data
if dict is not None:
self.update(dict)
if len(kwargs):
self.update(kwargs)
#print self.data #构造函数 def __repr__(self):#有该语句，a=UserDict(b)，print a时，可打印实例内容
return repr(self.data) def __cmp__(self, dict):
if isinstance(dict, UserDict):
return cmp(self.data, dict.data)
else:
return cmp(self.data, dict)
__hash__ = None # Avoid Py3k warning def __len__(self):
'''
给类构造长度运算方式，当a=UserDict(b)实例化时，print len(a)才能有运算结果
没有__len__语句，会报错，
如：AttributeError: UserDict instance has no attribute '__len__'
提示说明：UserDict instance(UserDict实例)没有__len__属性
'''
return len(self.data) def __getitem__(self, key):
if key in self.data:
return self.data[key]
if hasattr(self.__class__, "__missing__"):
return self.__class__.__missing__(self, key)
raise KeyError(key) def __setitem__(self, key, item):
'''
#__setitem__，不需要返回值，所以没有return
#怎么调用？
#a['a']=5
'''
self.data[key] = item #__delitem__，不需要返回值，所以没有return
def __delitem__(self, key):
'调用方式：del a[key]'
del self.data[key] def clear(self): self.data.clear() def copy(self):
if self.__class__ is UserDict:
return UserDict(self.data.copy())
import copy
data = self.data
try:
self.data = {}
c = copy.copy(self)
finally:
self.data = data
c.update(self)
return c def keys(self):
'''
>>> a.keys() #key键
['age', 'name', 'laiYuan']
'''
return self.data.keys()#注意data不能省略 def items(self):
return self.data.items() def iteritems(self):
return self.data.iteritems() def iterkeys(self):
return self.data.iterkeys() def itervalues(self):
return self.data.itervalues() def values(self):
'''
>>> a.values()
[28, 'xiaodeng', 'hubei']
'''
return self.data.values()
def has_key(self, key): return key in self.data #更新操作
def update(self, dict=None, **kwargs):
if dict is None:
pass
elif isinstance(dict, UserDict):
self.data.update(dict.data)
elif isinstance(dict, type({})) or not hasattr(dict, 'items'):
self.data.update(dict)
else:
for k, v in dict.items():
self[k] = v
if len(kwargs):
self.data.update(kwargs) def get(self, key, failobj=None):
'''
failobj：预定义内容，
该段小代码的意思是key是否在self中，如果不存在，则返回failobj，如存在可返回其value值
print a.get('name')#failobj用预定义的值None
print a.get('YuYan','python')
'''
if key not in self:
return failobj
return self[key] def setdefault(self, key, failobj=None):
'与get有异曲同工之妙'
if key not in self:
self[key] = failobj
return self[key] def pop(self, key, *args):
return self.data.pop(key, *args) def popitem(self):
'删除并返回dict中任意的一个(key,value)队，如果字典为空会抛出KeyError'
'KeyError:popitem(): dictionary is empty'
return self.data.popitem() def __contains__(self, key):
return key in self.data
@classmethod
def fromkeys(cls, iterable, value=None):
d = cls()
for key in iterable:
d[key] = value
return d
if __name__=='__main__':
b={'name':'xiaodeng','age':28,'laiYuan':'hubei'}
a=UserDict(b)
print a
print len(a)
print a.get('name')
print a.get('bb','python')