[SciPy-user] Python number handling?
oliphant at ee.byu.edu
Tue Aug 9 16:18:11 CDT 2005
Robert Kern wrote:
> Howey, David A wrote:
>> I'm new to python...
>> Why, why oh why did someone decide to make python do this:
>> Integer case
>> In : 107 / 4 Out: 26
>> Float case
>> In : 107.0 / 4
>> Out: 26.75
>> I'm a bit worried that when it come to using variables, because you
>> don't declare them (eg as integer or float) python might mess up
>> division and give you the first result above rather than the second.
>> Has anyone had any problems with this?
> Long, long ago, Guido decided to make integers behave this way because
> C integers behaved this way (close enough at any rate; Python differs
> from C with negative integers, but arguably does something more
> consistent). In many cases, this behavior is actually useful although
> it tends to get in the way a good amount of the time.
Robert is, as usual, spot on with his comments.
It should be noted that Python is moving towards having 107 / 4 return
the floating-point result while 107 // 4 will be integer division.
Note the following on Python 2.3.4
>>> 107 / 4
>>> from __future__ import division
>>> 107 / 4
I still think it is a good idea to use 4.0 when you mean to interpret 4
as a float.
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