格式:在字符串中使用大括号时出现 KeyError

Format: KeyError when using curly brackets in strings(格式:在字符串中使用大括号时出现 KeyError)

问题描述

我正在运行以下代码:

asset = {}
asset['abc'] = 'def'
print type(asset)
print asset['abc']
query = '{"abc": "{abc}"}'.format(abc=asset['abc'])
print query

这会引发 KeyError 错误:

[user@localhost] : ~/Documents/vision/inputs/perma_sniff $ python ~/test.py 
<type 'dict'>
def
Traceback (most recent call last):
  File "/home/user/test.py", line 5, in <module>
    query = '{"abc": "{abc}"}'.format(abc=asset['abc'])
KeyError: '"abc"'

格式显然被包装 { 弄糊涂了.如何确保格式仅尝试替换(正确的)内部 {abc}.

Format is obviously getting confused by the wrapping {. How can I make sure format only tries to replace the (correct) inner {abc}.

即，预期的输出是:

{"abc": "def"}

(我知道我可以使用 json 模块来完成这项任务，但我想避免这种情况.我更愿意使用格式.)

(I'm aware I could use the json module for this task, but I want to avoid that. I would much rather use format.)

推荐答案

要插入文字大括号，请将其加倍:

To insert a literal brace, double it up:

query = '{{"abc": "{abc}"}}'.format(abc=asset['abc'])

(在此处进行了记录，但没有特别明显地突出显示).

(This is documented here, but not highlighted particularly obviously).

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