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?
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.
Traceback (most recent call last): File "python", line 7, in <module> File "python", line 7, in <dictcomp> IndexError: tuple index out of range* to make a reference to the array for format values.
* has nothing to do with the reference/value distinction. It just expands the list to positional arguments. See docs.python.org/2/tutorial/….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?
You can use another formatting method:
'{"key1":"%s", "key2":"%s"}' % ("value1", "value2")
json.loadsjson.dumps.{number}is not a valid dictionary because it doesn't have any:'s in it.