cd in a function

• getcwd
• chdir

In this example we have a function in which we change to a directory and then when we are done we change back to the original directory. For this to work first we save the current working directory using the os.getcwd call. Unfortunatelly in the middle of the code there is a conditional call to return. If that condition is True we won't change back to the original directory. We could fix this by calling os.chdir(start_dir) just before calling return. However this would still not solve the problem if there is an exception in the function.

import sys
import os

def do_something(path):
    start_dir = os.getcwd()
    os.chdir(path)

    content = os.listdir()
    number = len(content)
    print(number)
    if number < 15:
        return

    os.chdir(start_dir)

def main():
    if len(sys.argv) != 2:
        exit(f"Usage: {sys.argv[0]} PATH")
    path = sys.argv[1]
    print(os.getcwd())
    do_something(path)
    print(os.getcwd())

main()

$ python no_context_cd.py /tmp/

/home/gabor/work/slides/python-programming/examples/advanced
19
/home/gabor/work/slides/python-programming/examples/advanced

$ python no_context_cd.py /opt/

/home/gabor/work/slides/python-programming/examples/advanced
9
/opt

• In the second example return was called and thus we stayed on the /opt directory.:w