Calling python script in bash script changes type of a variable

Question

I have a python script that at one point performs division. When I run the script normally from the command line, it treats the numbers as floats, and performs the correct division. i.e.

a = 2 
b = 5
print(a/b)
>0.4

I have also written a bash script that among other things, runs this same python script. When I run this bash script, python treats the numbers as integers, performs integer division, and returns zero. Why does this happen?

i.e.

a = 2 
b = 5
print(a/b) 
>0

EDIT:

python script

#!/usr/bin/python3

import sys
a = 2 
b = 5
print(sys.version)
print(a/b)

>3.5.2 (default, Nov 23 2017, 16:37:01) 
[GCC 5.4.0 20160609]
0.4

Bash script

python stack.py

>2.7.12 (default, Dec  4 2017, 14:50:18) 
[GCC 5.4.0 20160609]
0

Answer 1

Add a shebang line to the top of your script:

#!/usr/bin/python3

That will ensure that you get a consistent version of Python when it is run from a shell. Without this it appears bash is using Python2 where by default division of integers gives an integer result.