Why does this simple calculation return 0
>>> 25/100*50
0
while this actually calculates correctly?
>>> .25*50
12.5
>>> 10/2*2
10
What is wrong with the first example?
Asked
Active
Viewed 6.9k times
6 Answers
96
In Python 2, 25/100 is zero when performing an integer divison. since the result is less than 1.
You can "fix" this by adding from __future__ import division to your script. This will always perform a float division when using the / operator and use // for integer division.
Another option would be making at least one of the operands a float, e.g. 25.0/100.
In Python 3, 25/100 is always 0.25.
user2357112
- 260,549
- 28
- 431
- 505
ThiefMaster
- 310,957
- 84
- 592
- 636
-
automatically making a division 0? i just spent an hour debugging that – gary69 Apr 25 '20 at 18:39
-
google deep learning vm, the environment is all setup on python 2, locally i have python 3 and this was baffling me – gary69 Apr 25 '20 at 18:41
20
This is a problem of integer truncation (i.e., any fractional parts of a number are discarded). So:
25 / 100 gives 0
However, as long as at least one of the operands in the division is a float, you'll get a float result:
25 / 100.0 or 25.0 / 100 or 25.0 / 100.0 all give 0.25
Levon
- 138,105
- 33
- 200
- 191
-
How would one do this in case that the numbers are stored in a variable? For example x / y, where x = 4 and y = 3. Or x = someObject.size. – altabq Feb 05 '16 at 09:58
-
4One way to do it is tp multiply one of the numbers by 1.0. E.g., `1.0 * x / 2` or you could do `float(x) / 2` - there might be other ways, but these come to mind off the top of my head. You can always interactively verify your results before you code them up in a program. Hope that helps. – Levon Feb 05 '16 at 14:09
1
Python 2 returns zero for integer division if result is less than 1.
Solution is to convert one of the integers to float e.g.
float(25)/100*50
Ndheti
- 266
- 3
- 18
