how to execute 7zip commands from python script

Question

I am trying to get a basic idea of how the os.system module can be used to execute 7zip commands. For now I don't want to complicate things with Popen or subprocess. I have installed 7zip and copied the 7zip.exe into my users folder. I just want to extract my test file install.zip. However using the code below causes the shell to appear briefly before exiting and no unzip has occurred. Please could you tell me why?

def main():
    try:

         os.system(r"C:\Users\Oulton\ 7z e C:\Users\Oulton\install.zip")
    except:
            time.sleep(3)
            traceback.print_exc

if __name__ == "__main__":
    main()

Many Thanks

Answer 1

Can be done using sub process module:

import subprocess

beforezip = D:\kr\file                         #full location
afterzip = filename.zip
Unzipped_file = "7z a \"%s\" \"%s\"" %( afterzip, beforezip )
retV = subprocess.Popen(cmdExtractISO, shell=True, stdout=subprocess.PIPE, 
stderr=subprocess.STDOUT)
outData = retV.stdout.readlines();

Answer 2

There are several problems with the following line:

os.system("C:\Users\Oulton\ 7z e C:\Users\Oulton\install.zip  ")

Since your string contains backslashes, you should use a raw string:

os.system(r"C:\Users\Oulton\7z -e C:\Users\Oulton\install.zip")

(note the r before the first double quote.)

I've also removed the extraneous spaces. The first one (before the 7z) was definitely problematic.

Also note that the traceback.print_exc does not call the function. You need to add parentheses: traceback.print_exc().

Finally, it is recommended that in new code the subprocess module is used in preference to os.system().