python学习笔记（第二天）

1、字典复制：

dict = {‘name‘:‘wang‘, ‘sex‘:‘m‘, ‘age‘:34, ‘job‘:‘it‘}

info = dict            ##别名 （二个字典指向内存的同一地址空间）

info1 = dict.copy()    #shadow copy 浅复制（嵌套字典第一层独立，第二层以下相关联）

import copy

copy.copy()            #shadow copy 浅复制

copy.deepcopy()        #deep copy   深复制（完全独立）

注：浅复制下的关联只是针对字典初始状态包含的嵌套对象，后新加的不会

例：

>>> dict
{‘info‘: [‘a‘, ‘b‘, 1, 2], ‘job‘: ‘it‘, ‘sex‘: ‘m‘, ‘age‘: 40, ‘name‘: ‘wang‘}
>>> dict_alias = dict
>>> dict_copy = copy.copy(dict)
>>> dict_deep = copy.deepcopy(dict)

#添加、改变、删除第一层的对象键值，浅复制和深复制都不受影响

>>> dict[‘age‘] = 32

>>> del dict[‘sex‘]
>>> dict
{‘info‘: [‘a‘, ‘b‘, 1, 2], ‘job‘: ‘it‘, ‘age‘: 32, ‘name‘: ‘wang‘}
>>> dict_alias     
{‘info‘: [‘a‘, ‘b‘, 1, 2], ‘job‘: ‘it‘, ‘age‘: 32, ‘name‘: ‘wang‘}
>>> dict_copy      
{‘info‘: [‘a‘, ‘b‘, 1, 2], ‘job‘: ‘it‘, ‘age‘: 40, ‘name‘: ‘wang‘, ‘sex‘: ‘m‘}
>>> dict_deep      
{‘info‘: [‘a‘, ‘b‘, 1, 2], ‘job‘: ‘it‘, ‘age‘: 40, ‘name‘: ‘wang‘, ‘sex‘: ‘m‘}

#改变、删除原有的第二层的对象键值，浅复制受影响，而深复制都不受影响

>>> dict[‘info‘][2] = 100
>>> dict
{‘info‘: [‘a‘, ‘b‘, 100, 2], ‘job‘: ‘it‘, ‘age‘: 32, ‘name‘: ‘wang‘}
>>> dict_alias
{‘info‘: [‘a‘, ‘b‘, 100, 2], ‘job‘: ‘it‘, ‘age‘: 32, ‘name‘: ‘wang‘}
>>> dict_copy
{‘info‘: [‘a‘, ‘b‘, 100, 2], ‘job‘: ‘it‘, ‘age‘: 40, ‘name‘: ‘wang‘, ‘sex‘: ‘m‘}
>>> dict_deep
{‘info‘: [‘a‘, ‘b‘, 1, 2], ‘job‘: ‘it‘, ‘age‘: 40, ‘name‘: ‘wang‘, ‘sex‘: ‘m‘}

#添加第二层的对象，浅复制和深复制都不受影响

>>> dict[‘new‘] = {‘a‘:1, ‘b‘:2, ‘c‘:5}
>>> dict
{‘info‘: [‘a‘, ‘b‘, 100, 2], ‘name‘: ‘wang‘, ‘age‘: 32, ‘job‘: ‘it‘, ‘new‘: {‘a‘: 1, ‘c‘: 5, ‘b‘: 2}}
>>> dict_alias
{‘info‘: [‘a‘, ‘b‘, 100, 2], ‘name‘: ‘wang‘, ‘age‘: 32, ‘job‘: ‘it‘, ‘new‘: {‘a‘: 1, ‘c‘: 5, ‘b‘: 2}}
>>> dict_copy
{‘info‘: [‘a‘, ‘b‘, 100, 2], ‘job‘: ‘it‘, ‘age‘: 40, ‘name‘: ‘wang‘, ‘sex‘: ‘m‘}
>>> dict_deep
{‘info‘: [‘a‘, ‘b‘, 1, 2], ‘job‘: ‘it‘, ‘age‘: 40, ‘name‘: ‘wang‘, ‘sex‘: ‘m‘}

2、内置函数说明:

      __name__：主文件时返回main，否则返回文件名，可用来判断是否说主文件还是导入模块；

      __file__：文件的绝对路径；

      __doc__：文件开头的注释说明

例：

‘‘‘
    created by 2015-12-18
    @author: kevin
‘‘‘

if __name__ == ‘__main__‘:
    print(‘this is main file‘)
    print(__file__)
    print(__doc__)

python学习笔记（第二天）

原文：http://www.cnblogs.com/wushank/p/5060023.html