本文介绍了字符串格式JSON字符串给出KeyError的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!

问题描述

为什么这段代码给出一个 KeyError

  output_format = 
{
File:{filename},
Success:{success},
ErrorMessage:{error_msg},
LogIdentifier:{log_identifier}
}


print output_format.format(filename ='My_file_name',
success =
error_msg ='',
log_identifier ='123')

错误讯息:

  KeyError:'File'


解决方案

您需要将外括号加倍;否则Python认为 {File.. 也是一个引用:

  output_format ='{{File:{filename},Success:{success},ErrorMessage:{error_msg},LogIdentifier:{log_identifier}}}'




$ p $ >>>> print_format.format(filename ='My_file_name',
... success = True,
... error_msg ='',
... log_identifier ='123')
{File:My_file_name,Success:True,ErrorMessage:,LogIdentifier:123}

如果您显然是在生成JSON输出,那么最好使用: > import json
>>>打印json.dumps(Dict(File ='My_file_name',
... Success = True,
... ErrorMessage ='',
... LogIdentifier ='123'))
{LogIdentifier:123,ErrorMessage:,Success:true,File:My_file_name}
小写 true ,正如JSON标准所要求的那样。
p>

Why does this code give a KeyError?

output_format = """
{
    "File": "{filename}",
    "Success": {success},
    "ErrorMessage": "{error_msg}",
    "LogIdentifier": "{log_identifier}"
}
"""

print output_format.format(filename='My_file_name',
                           success=True,
                           error_msg='',
                           log_identifier='123')

Error message:

KeyError: ' "File"'
解决方案

You need to double the outer braces; otherwise Python thinks { "File".. is a reference too:

output_format = '{{ "File": "{filename}", "Success": {success}, "ErrorMessage": "{error_msg}", "LogIdentifier": "{log_identifier}" }}'

Result:

>>> print output_format.format(filename='My_file_name',
...                            success=True,
...                            error_msg='',
...                            log_identifier='123')
{ "File": "My_file_name", "Success": True, "ErrorMessage": "", "LogIdentifier": "123" }

If, indicentally, you are producing JSON output, you'd be better off using the json module:

>>> import json
>>> print json.dumps(dict(File='My_file_name',
...                            Success=True,
...                            ErrorMessage='',
...                            LogIdentifier='123'))
{"LogIdentifier": "123", "ErrorMessage": "", "Success": true, "File": "My_file_name"}

Note the lowercase true in the output, as required by the JSON standard.

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08-05 08:09