[Python-Dev] TypeError: f() missing 1 required positional argument: 'x'

Mark Dickinson dickinsm at gmail.com
Thu Sep 20 14:59:16 CEST 2012

On Thu, Sep 20, 2012 at 1:21 PM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> +1 for using the unqualified "argument" in these error messages to
> mean "positional or keyword argument" (inspect.Parameter spells it out
> as POSITIONAL_OR_KEYWORD, but the full phrase is far too verbose for
> an error message).

Ah yes;  I see that 'positional or keyword' is a more accurate term
(but agree it's unwieldy for an error message).  I also see that I was
naive to think that the 'fix' is as simple as dropping the word

    >>> def f(a, *, b):
    ...     pass
    >>> f()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    TypeError: f() missing 1 required positional argument: 'a'

If the word 'positional' were dropped here, it would give the
incorrect impression that f only requires one argument.

Perhaps this simply isn't worth worrying about, especially since the
current error messages are all but certain to make it into the 3.3


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