标签：item shel python 迭代 类对象 recent 键值 mos self
1.dict方法概述
In[70]: dir(dict) Out[69]: [‘__class__‘, ‘__contains__‘, ‘__delattr__‘, ‘__delitem__‘, ‘__dir__‘, ‘__doc__‘, ‘__eq__‘, ‘__format__‘, ‘__ge__‘, ‘__getattribute__‘, ‘__getitem__‘, ‘__gt__‘, ‘__hash__‘, ‘__init__‘, ‘__init_subclass__‘, ‘__iter__‘, ‘__le__‘, ‘__len__‘, ‘__lt__‘, ‘__ne__‘, ‘__new__‘, ‘__reduce__‘, ‘__reduce_ex__‘, ‘__repr__‘, ‘__setattr__‘, ‘__setitem__‘, ‘__sizeof__‘, ‘__str__‘, ‘__subclasshook__‘, ‘clear‘, ‘copy‘, ‘fromkeys‘, ‘get‘, ‘items‘, ‘keys‘, ‘pop‘, ‘popitem‘, ‘setdefault‘, ‘update‘, ‘values‘]
2.copy()：
dict.copy()——返回一个新的（浅拷贝）——列表这类复杂数据需要深拷贝。。
3.clear()
清空字典中所有元素 同 b={}
In[86]: b Out[85]: {‘age‘: 26, ‘name‘: ‘ddd‘, ‘university‘: ‘shanghaicaijing‘} In[87]: b.clear() In[88]: b Out[87]: {} In[89]: b={}
4.items,keys,values
分别返回字典中的类似集合类对象。有迭代行，用来遍历方便。
In[91]: city2 Out[90]: {‘fifth‘: [‘zhengzhou‘, ‘hefei‘, ‘wuhan‘], ‘first‘: ‘beijing‘, ‘forth‘: ‘shenzhen‘, ‘second‘: ‘shanghai‘} In[92]: city2.items() Out[91]: dict_items([(‘first‘, ‘beijing‘), (‘second‘, ‘shanghai‘), (‘forth‘, ‘shenzhen‘), (‘fifth‘, [‘zhengzhou‘, ‘hefei‘, ‘wuhan‘])]) In[93]: city2.keys() Out[92]: dict_keys([‘first‘, ‘second‘, ‘forth‘, ‘fifth‘]) In[94]: city2.values() Out[93]: dict_values([‘beijing‘, ‘shanghai‘, ‘shenzhen‘, [‘zhengzhou‘, ‘hefei‘, ‘wuhan‘]]) In[95]: for i in city2.keys(): ... print(i) ... first second forth fifth
5.删除方法——pop() & popitem()
pop()——删除该键值对，并返回值。如果没有该键，可以返回信息或报错。
In[96]: city Out[95]: {‘first‘: ‘beijing‘, ‘second‘: ‘shanghai‘} In[97]: city.pop(‘third‘,‘未有{0}项‘.format(‘third‘)) Out[96]: ‘未有third项‘ In[98]: city.pop(‘first‘) Out[97]: ‘beijing‘
popitem()————随机删除，无需参数，返回类型为数组，空数组报错。
In[99]: help(dict.popitem) Help on method_descriptor: popitem(...) D.popitem() -> (k, v), remove and return some (key, value) pair as a 2-tuple; but raise KeyError if D is empty.
In[102]: city3 Out[101]: {‘fifth‘: [‘zhengzhou‘, ‘hefei‘, ‘wuhan‘], ‘first‘: ‘beijing‘, ‘forth‘: ‘shenzhen‘, ‘second‘: ‘shanghai‘} In[103]: city3.popitem() Out[102]: (‘fifth‘, [‘zhengzhou‘, ‘hefei‘, ‘wuhan‘]) In[104]: city3.clear() In[105]: city3.popitem() Traceback (most recent call last): File "C:\ProgramData\Anaconda3\lib\site-packages\IPython\core\interactiveshell.py", line 2881, in run_code exec(code_obj, self.user_global_ns, self.user_ns) File "<ipython-input-104-c47179c00790>", line 1, in <module> city3.popitem() KeyError: ‘popitem(): dictionary is empty‘
6. 更新字典——update()
In[107]: help(dict.update) Help on method_descriptor: 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]
dict.update(可迭代对象/字典2)————无返回值，增加字典2中的内容到字典中
In[108]: a Out[107]: {‘age‘: 26, ‘name‘: ‘eric‘, ‘number‘: ‘201521234‘, ‘university‘: ‘CUP‘} In[109]: city2 Out[108]: {‘fifth‘: [‘zhengzhou‘, ‘hefei‘, ‘wuhan‘], ‘first‘: ‘beijing‘, ‘forth‘: ‘shenzhen‘, ‘second‘: ‘shanghai‘} In[110]: a.update(city2) In[111]: a Out[110]: {‘age‘: 26, ‘fifth‘: [‘zhengzhou‘, ‘hefei‘, ‘wuhan‘], ‘first‘: ‘beijing‘, ‘forth‘: ‘shenzhen‘, ‘name‘: ‘eric‘, ‘number‘: ‘201521234‘, ‘second‘: ‘shanghai‘, ‘university‘: ‘CUP‘}
标签：item shel python 迭代 类对象 recent 键值 mos self
原文地址：http://www.cnblogs.com/song-raven/p/7197549.html
