Format string unused named arguments [duplicate]

If you are using Python 3.2+, use can use str.format_map().

For bond, bond:

>>> from collections import defaultdict>>> '{bond}, {james} {bond}'.format_map(defaultdict(str, bond='bond'))'bond,  bond'

For bond, {james} bond:

>>> class SafeDict(dict):...     def __missing__(self, key):...         return '{' + key + '}'...>>> '{bond}, {james} {bond}'.format_map(SafeDict(bond='bond'))'bond, {james} bond'

In Python 2.6/2.7

For bond, bond:

>>> from collections import defaultdict>>> import string>>> string.Formatter().vformat('{bond}, {james} {bond}', (), defaultdict(str, bond='bond'))'bond,  bond'

For bond, {james} bond:

>>> from collections import defaultdict>>> import string>>>>>> class SafeDict(dict):...     def __missing__(self, key):...         return '{' + key + '}'...>>> string.Formatter().vformat('{bond}, {james} {bond}', (), SafeDict(bond='bond'))'bond, {james} bond'

You could use a template string with the safe_substitute method.

from string import Templatetpl = Template('$bond, $james $bond')action = tpl.safe_substitute({'bond': 'bond'})

You can follow the recommendation in PEP 3101 and subclass Formatter:

from __future__ import print_functionimport stringclass MyFormatter(string.Formatter):    def __init__(self, default='{{{0}}}'):        self.default=default    def get_value(self, key, args, kwds):        if isinstance(key, str):            return kwds.get(key, self.default.format(key))        else:            return string.Formatter.get_value(key, args, kwds)

Now try it:

>>> fmt=MyFormatter()>>> fmt.format("{bond}, {james} {bond}", bond='bond', james='james')'bond, james bond'>>> fmt.format("{bond}, {james} {bond}", bond='bond')'bond, {james} bond'

You can change how key errors are flagged by changing the text in self.default to what you would like to show for KeyErrors:

>>> fmt=MyFormatter('">>{{{0}}} KeyError<<"')>>> fmt.format("{bond}, {james} {bond}", bond='bond', james='james')'bond, james bond'>>> fmt.format("{bond}, {james} {bond}", bond='bond')'bond, ">>{james} KeyError<<" bond'

The code works unchanged on Python 2.6, 2.7, and 3.0+