Why use Python's os module methods instead of executing shell commands directly?

Question

I am trying to understand what is the motivation behind using Python\'s library functions for executing OS-specific tasks such as creating files/directories, changing file attri

Answer 1

For a simple reason - when you call a shell function, it creates a sub-shell which is destroyed after your command exists, so if you change directory in a shell - it does not affect your environment in Python.

Besides, creating sub-shell is time consuming, so using OS commands directly will impact your performance

EDIT

I had some timing tests running:

In [379]: %timeit os.chmod('Documents/recipes.txt', 0755)
10000 loops, best of 3: 215 us per loop

In [380]: %timeit os.system('chmod 0755 Documents/recipes.txt')
100 loops, best of 3: 2.47 ms per loop

In [382]: %timeit call(['chmod', '0755', 'Documents/recipes.txt'])
100 loops, best of 3: 2.93 ms per loop

Internal function runs more than 10 time faster

EDIT2

There may be cases when invoking external executable may yield better results than Python packages - I just remembered a mail sent by a colleague of mine that performance of gzip called through subprocess was much higher than the performance of a Python package he used. But certainly not when we are talking about standard OS packages emulating standard OS commands