python如何将一串字符串转换为字典

python中将字符串转换为字典的方法：

1、通过 json 来转换

>>>importjson
>>>user_info='{"name":"john","gender":"male","age":28}'
>>>user_dict=json.loads(user_info)
>>>user_dict
{u'gender':u'male',u'age':28,u'name':u'john'}

由于json语法规定数组或对象之中的字符串必须使用双引号，不能使用单引号(官网上有一段描述是 “A string is a sequence of zero or more Unicode characters, wrapped in double quotes, using backslash escapes” )，因此下面的转换是错误的：

>>>importjson
>>>user_info="{'name':'john','gender':'male','age':28}"
#由于字符串使用单引号，会导致运行出错
>>>user_dict=json.loads(user_info)
Traceback(mostrecentcalllast):
File"<stdin>",line1,in<module>
File"/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/__init__.py",line339,inloads
return_default_decoder.decode(s)
File"/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.py",line364,indecode
obj,end=self.raw_decode(s,idx=_w(s,0).end())
File"/usr/local/Cellar/python/2.7.11/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/decoder.py",line380,inraw_decode
obj,end=self.scan_once(s,idx)
ValueError:Expectingpropertyname:line1column2(char1)

2、通过 eval转换

>>>usr_info='{"name":"john","gender":"male","age":28}'
>>>user_dict=eval(user_info)
>>>user_dict
{'gender':'male','age':28,'name':'john'}
>>>user_info="{'name':'john','gender':'male','age':28}"
>>>user_dict=eval(user_info)
>>>user_dict
{'gender':'male','age':28,'name':'john'}

通过eval进行转换就不存在上面使用json进行转换的问题。但是，使用eval却存在安全性的问题，比如下面的例子:

#让用户输入`user_info`
>>>user_info=raw_input('inputuserinfo:')
#输入{"name":"john","gender":"male","age":28}，没问题
>>>user_dict=eval(user_info)
#输入__import__('os').system('dir')，user_dict会列出当前的目录文件！
#再输入一些删除命令，则可以把整个目录清空了！
>>>user_dict=eval(user_info)

3、通过 literal_eval转换

>>>importast
>>>user='{"name":"john","gender":"male","age":28}'
>>>user_dict=ast.literal_eval(user)
>>>user_dict
{'gender':'male','age':28,'name':'john'}
user_info="{'name':'john','gender':'male','age':28}"
>>>user_dict=ast.literal_eval(user)
>>>user_dict
{'gender':'male','age':28,'name':'john'}