I am formatting strings using named arguments with .format(). How can I obtain a list of arguments?
For example:
>>> my_string = 'I live in {city}, {state}, {country}.'
>>> get_format_args(my_string)
# ['city', 'state', 'country']
Note that order does not matter. I have dug a fair amount into the string.Formatter documentation to no avail. I am sure you could write regex to do this, but there must bet a more elegant way.
It looks like you can get field names using the Formatter.parse method:
>>> import string
>>> my_string = 'I live in {city}, {state}, {country}.'
>>> [tup[1] for tup in string.Formatter().parse(my_string) if tup[1] is not None]
['city', 'state', 'country']
This will also return non-named arguments. Example: "{foo}{1}{}" will return ['foo', '1', '']. But if necessary you can filter out the latter two by using str.isdigit() and comparing against the empty string respectively.
string.Formatter.parseRegex can solve your problem.
>>> import re
>>> re.findall(r'{(.*?)}', 'I live in {city}, {state}, {country}.')
['city', 'state', 'country']
Edit:
To avoid matching escaped placeholders like '{{city}}' you should change your pattern to something like:
(?<=(?<!\{)\{)[^{}]*(?=\}(?!\}))
(?<= # Assert that the following can be matched before the current position (?<!\{) # (only if the preceding character isn't a {) \{ # a { ) # End of lookbehind [^{}]* # Match any number of characters except braces (?= # Assert that it's possible to match... \} # a } (?!\}) # (only if there is not another } that follows) ) # End of lookahead
'{{city}}'
'{0:{fill}{align}16}'