python的setdefault方法
2016-04-25 17:12
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setdefault(key[, default])
If key is in the dictionary, return its value. If not, insert key with a value of default and
return default. default defaults to None.
如果键在字典中,返回这个键所对应的值。如果键不在字典中,向字典 中插入这个键,并且以default为这个键的值,并返回 default。default的默认值为None
Python 2.5.4 (r254:67916, Dec 23 2008, 15:19:34) [MSC v.1400 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
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makes to its subprocess using this computer's internal loopback
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IDLE 1.2.4
>>> dict={}
>>> dict['key']='a'
>>> dict
{'key': 'a'}
>>> dict.setdefault('key', 'b') # 键key存在,故返回简直a.
'a'
>>> dict
{'key': 'a'}
>>> dict.setdefault('key0', 'b') # 键key0不存在,故插入此键,并以b为键值.
'b'
>>> dict
{'key0': 'b', 'key': 'a'}
>>>
If key is in the dictionary, return its value. If not, insert key with a value of default and
return default. default defaults to None.
如果键在字典中,返回这个键所对应的值。如果键不在字典中,向字典 中插入这个键,并且以default为这个键的值,并返回 default。default的默认值为None
Python 2.5.4 (r254:67916, Dec 23 2008, 15:19:34) [MSC v.1400 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
****************************************************************
Personal firewall software may warn about the connection IDLE
makes to its subprocess using this computer's internal loopback
interface. This connection is not visible on any external
interface and no data is sent to or received from the Internet.
****************************************************************
IDLE 1.2.4
>>> dict={}
>>> dict['key']='a'
>>> dict
{'key': 'a'}
>>> dict.setdefault('key', 'b') # 键key存在,故返回简直a.
'a'
>>> dict
{'key': 'a'}
>>> dict.setdefault('key0', 'b') # 键key0不存在,故插入此键,并以b为键值.
'b'
>>> dict
{'key0': 'b', 'key': 'a'}
>>>
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