python import fails when called from PHP

Question

I'm having a puzzling problem when trying to import a module in python only when the script is called from php via system or exec.

From the python shell:

import igraph #This works.

if the previous line was in a file, say, test_module.py, then:
python test_module.py in the bash works.

Within PHP:
exec("python test_module.py",$output,$retval) -> fails : $retval = 1.

However, if the script is instead : import math, then this is fine.

Anybody ever dealt with something similar?

Answer 1

one thing to check is sys.path

see what the difference is when called each way