I have this simple code:
[n/2 for n in range(100, 200)]
But, strangely enough, it returns [50,50,51,51,52,52,etc], so it uses integer division instead of normal one (I need it to output [50,50.5,51,51.5,etc]) Why is it happening?
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2 Answers
In Python 2, dividing 2 integers will always produce an integer. (In Python 3, you get "real" division)
You can rewrite your code as:
[n/2.0 for n in range(100, 200)]
or in the case where you have 2 variables:
[float(n)/othervar for n in range(100, 200)]
to get the expected behavior,
or add
from __future__ import division
at the start of the file to get the Python 3 behavior now.
To answer the "why" part of the question, this is a holdover from C's division semantics (although Python made the choice to always floor the result instead of rounding toward 0, so you don't even get the true C integer division semantics.)
4 Comments
hanleyhansen
Nice contribution with the
__future__ module.
RomaValcer
Yeah, apparently I have to use n/(variable+0.00). That works, but it's not looking good.
Wooble
@RomaValcer: edited my answer. use
float() on either of the variables rather than adding 0.00 to force one to be a float.RomaValcer
yeah, looks much better. Anyways, sometimes python dynamic typization (if I chose right word) can cause trouble.
Try [n/2.0 for n in range(100, 200)] to make it a float operation. By passing 2 as an integer and all numbers in the range as an integer Python is treating the result as an integer. You need Floating Point Arithmetic. See here for more details.
