[Python-Dev] return type of complex (original) (raw)

Chris Angelico rosuav at gmail.com
Sun Oct 21 14:06:45 CEST 2012

On Sun, Oct 21, 2012 at 10:08 PM, Antoine Pitrou <solipsis at pitrou.net> wrote:

On Sun, 21 Oct 2012 22:02:17 +1100 Steven D'Aprano <steve at pearwood.info> wrote:

In Python 3.3, math.pow is the builtin pow. Presumably for backwards compatibility reasons when they were different? If so, it was a LONG time ago: [steve at ando ~]$ python1.5 Python 1.5.2 (#1, Aug 27 2012, 09:09:18) [GCC 4.1.2 20080704 (Red Hat 4.1.2-52)] on linux2 Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam >>> import math >>> math.pow You are being too optimistic:

pow math.pow pow is math.pow False

The one in math doesn't take three args.

Python 3.2 (r32:88445, Feb 20 2011, 21:29:02) [MSC v.1500 32 bit (Intel)] on win32

math.pow(1,2,3) Traceback (most recent call last): File "<pyshell#3>", line 1, in math.pow(1,2,3) TypeError: pow expected 2 arguments, got 3

I conducted a brief survey of a non-technical nature (that is to say, I rambled to my brother and listened to what he said in response), and he's of the opinion that many programmers would be surprised and confused by the sudden appearance of complex numbers in programs that weren't using them. On the flip side, it's kinda like a NaN - you don't get an error immediately, but you'll either see it in your output or get an exception later on.

His suggestion was that an expression unexpectedly returning a complex should issue a warning. Warnings aren't really useful in Python as most people have them off, but would there be any way that this sort of thing could be caught by a linter? It'd probably require some fairly deep code analysis to figure out that you're taking the square root of something that could be negative, though.

ChrisA

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