(original) (raw)

so as far as I can tell, the only way you could accidentally get a   
complex number without expecting one is by exponentiation, either by \*\*   
or the builtin pow. This includes square roots. Exponentiation isn't as   
common as the basic four arithmetic operators, but it is hardly exotic.

Any time you have a non-integer power and a negative base, you will get
a complex number.

% python3

Python 3.3.0 (default, Sep 29 2012, 22:42:55)

[GCC 4.6.3] on linux

Type "help", "copyright", "credits" or "license" for more
information.

>>> import math

>>> pow(-1, 0.5)

(6.123031769111886e-17+1j)

>>> -1 ** 0.5

-1.0

>>> math.pow(-1, 0.5)

Traceback (most recent call last):

File "", line 1, in

ValueError: math domain error

>>>