code works in python shell, but not in a terminal

[Gribouillis]

We'll try to see if there is an invisible hidden character in the source file. Try this in a python shell,
in a directory containing the script

>>> for line in open('putPicsinColumn1version4.py'):
...     print(repr(line))
...

Then look around 'for sheet in sheets' in the output to see if there is something special there. Hidden characters may appear when someone copies and pastes a section of code from a pdf file into a code editor for example.