Python 3.2+Strings (str)function

str.format_map

formatting

Like format, but take substitutions directly from a mapping (no copy).

Syntax

s.format_map(mapping)

The point is not just that the mapping is not copied: format_map accepts any mapping, so you can pass a collections.defaultdict or your own class with __missing__ and have absent keys fall back to a placeholder instead of blowing up. With a plain dict a missing key still raises KeyError.

Examples

print('{x}!'.format_map({'x': 'ok'}))          # → ok!
print('{a}-{b}'.format_map({'a': 1, 'b': 2}))  # → 1-2
print('{name}'.format_map({'name': 'Аня'}))    # → Аня

See also

Common errors

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