[issue33669] str.format should raise exception when placeholder number doesn't match argument number

[Serhiy Storchaka]

Serhiy Storchaka <storchaka+cpython at gmail.com> added the comment:

This will break the following case:

def geterrmsg(n):
    return ('function doesn't have arguments' if n == 0 else
            'function have a single argument' if n == 1 else
            'function have %d arguments')

print(geterrmsg(n).format(n))

Actually geterrmsg() can take the error message from a translations database, and the number of different cases can be dependent on the language.

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nosy: +serhiy.storchaka

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<https://bugs.python.org/issue33669>
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