如何在Python中格式化JSON字符串

Question

I have a number of string with json format such as '{"key1":{0}, "key2":{1}}' .

After I retrieve the json string and substitute with values. '{"key1":{0}, "key2":{1}}'.format("value1", "value2") . # KeyError: '"key1"

The problem is caused by the bracket { , and I should use {{ and }} in the string, however, it is not easy to add { to the the string because the bracket may appear in the middle part such as '{"key1":{0}, "key2":{1}, "{3}":"value3"}'

How can I format the json string?

Answer 1

If you are building these strings yourself or have control over them, have a different format be sent, or build the value as a dictionary and use json.dumps .

However, if you really need to do this, if it's guaranteed that the substitution values will be in the format {X} , then you can escape the string with this kludge:

import re
s = '{"key1":{0}, "key2":{1}}'
begin = re.compile(r'{(?!\d)')
end = re.compile(r'(?<!\d)}')
escaped = end.sub('}}', begin.sub('{{', s))
print(escaped.format(1, 2))

results in

{"key1":1, "key2":2}

Note that this is not the best solution. Considering you have control of the strings, you should be escaping them in some other way. Maybe use the % syntax instead of str.format ?

Answer 2

Don't try to manipulate the data as an encoded string. Decode the JSON before trying to apply the formatting.

import json

json_data = '{"key1":"{0}","key2":"{1}"}'
format_args = ["value1", "value2"]

data = json.loads(json_data)
formatted_data = {key: value.format(*format_args) for key, value in data.items()}

You can then re-encode the formatted data as JSON if need be.