Why does str.split not take keyword arguments?

Question

I came across this - in my view - strange behaviour:

"a b c".split(maxsplit=1)
TypeError: split() takes no keyword arguments

Why does str.split() not take keyword arguments, even though it would make sense? I found this behavior both in Python2 and Python3.

Python 3.6 works. Please specify which version of Python 3.x didn't? Only 2.x (2.5 .. 2.7) seem to exhibit this. [Issue 1176](https://bugs.python.org/issue1176) — smci, Sep 03 '18 at 07:18

score 32 · Accepted Answer · answered Jul 30 '12 at 07:07

32

See this bug and its superseder.

str.split() is a native function in CPython, and as such exhibits the behavior described here:

CPython implementation detail: An implementation may provide built-in functions whose positional parameters do not have names, even if they are ‘named’ for the purpose of documentation, and which therefore cannot be supplied by keyword. In CPython, this is the case for functions implemented in C that use PyArg_ParseTuple() to parse their arguments.

answered Jul 30 '12 at 07:07

Frédéric Hamidi

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In the interest of self-documenting code, this is a shame. – Bob Stein May 22 '17 at 12:54
`range` also has this problem. – Jingguo Yao Jun 21 '18 at 06:08

score 15 · Answer 2 · answered Jul 30 '12 at 07:07

15

str.split is a builtin method implemented in C. Unfortunately some builtin functions/methods do not accept keyword arguments. See this bug report.

answered Jul 30 '12 at 07:07

BrenBarn

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Why does str.split not take keyword arguments?

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