New submission from Andrew Dalke <[email protected]>:
complex("nan") raises "ValueError: complex() arg is a malformed string" while
complex(float("nan")) returns (nan+0j). This was reported in
http://bugs.python.org/issue2121 with the conclusion "wont fix".
complex("inf") has the same behaviors.
The implementation in complexobject.c says
/* a valid complex string usually takes one of the three forms:
<float> - real part only
<float>j - imaginary part only
<float><signed-float>j - real and imaginary parts
where <float> represents any numeric string that's accepted by the
float constructor (including 'nan', 'inf', 'infinity', etc.), and
<signed-float> is any string of the form <float> whose first
character is '+' or '-'.
This comment is wrong and it distracted me for a while as I tried to figure out
why complex("nan") wasn't working. It should be fixed, with the word
"including" replaced by "excluding".
I don't have a real need for complex("nan") support - this was of intellectual
interest only. Also of intellectual interest, PyPy 1.4 does accept
complex("nan") but converts complex("nan+nanj") to (nannanj), so it suffers
from the strange corner cases which Raymond points out when advocating for
"wont fix."
Because
----------
assignee: d...@python
components: Documentation
messages: 125104
nosy: dalke, d...@python
priority: normal
severity: normal
status: open
title: complex() comments wrongly say it supports NaN and inf
versions: Python 2.7
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<http://bugs.python.org/issue10809>
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