Is there a complete list of built-in functions that cannot be called with keyword argument?

Question

People mentioned in answers a1, a2 that

Due to the way the Python C-level APIs developed, a lot of built-in functions and methods don't actually have names for their arguments.

I found it really annoying cause I'm not be able to know it by looking at the doc. For instance, eval

eval(expression, globals=None, locals=None)

Then I wrote this line of code

print(eval('a+b', globals={'a':1, 'b':2}))

and got TypeError: eval() takes no keyword arguments. So is there a complete list of functions of this kind? How do I know if a function is allowed to have keyword arguments?

Not only that but there are bugs with this, try `sorted(iterable=[])` vs `sorted(iterable=None)`. — Antti Haapala -- Слава Україні, Apr 14 '16 at 08:38
I guess that all such "traps" are actually bugs, and should be reported: both ``sorted()`` and the keyword arguments documented but not accepted. (Fwiw PyPy generally accepts keyword arguments.) — Armin Rigo, Apr 14 '16 at 08:40
It has been reported IIRC. (I think I read it from the bug tracker) — Antti Haapala -- Слава Україні, Apr 14 '16 at 08:41
@ArminRigo What's more disappointing is that this isn't even mentioned in doc. — laike9m, Apr 14 '16 at 08:42

score 4 · Accepted Answer · answered Apr 14 '16 at 08:45

In Python 3.5 you can inspect the __text_signature__ of the built-in function:

>>> eval.__text_signature__
'($module, source, globals=None, locals=None, /)'

or

>>> abs.__text_signature__
'($module, x, /)'
>>> abs(x=5)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: abs() takes no keyword arguments

(x cannot be used as a keyword argument)

The / means that the arguments following that can be used as keyword arguments. C.f.

>>> compile.__text_signature__
'($module, /, source, filename, mode, flags=0,\n        dont_inherit=False, optimize=-1)'
>>> compile(source='foo', filename='bar', mode='exec')
<code object <module> at 0x7f41c58f0030, file "bar", line 1>

Of course there are bugs even in 3.5:

>>> sorted.__text_signature__
'($module, iterable, key=None, reverse=False)'

though according to issue 26729 in the Python bug tracker, there ought to be / after the iterable as the iterable cannot be used as a keyword argument.

Unfortunately this information is not yet available in the Python documentation itself.

Is there a complete list of built-in functions that cannot be called with keyword argument?

1 Answers1