Is it good style to call bash commands within a Python script using os.system("bash code")? [closed]

Question

I was wondering whether or not it is considered a good style to call bash commands within a Python script using os.system(). I was also wondering whether or not it is safe to do so as well.

I know how to implement some of the functionality I need in Bash and in Python, but it is much simpler and more intuitive to implement it in Bash. However, I feel like it is very hackish to write os.system("bash code").

Specifically, I want to move all files that end with a certain extension to a directory.

In bash: *mv .ext /path/to/destination In Python (Pseudocode): for file in directory: if file.endswith("ext"): move file to destination

In this case, what should I do?

Answer 1

First of all, your example uses mv, which is a program in coreutils, not bash.

Using os.system() calls to external programs is considered poor style because:

• You are creating platform-specific dependencies
• You are creating version-specific dependencies (Yes, even coreutils change sometimes!)
• You need to check for the existence of external commands (and that they are in $PATH, and executable by the user etc.)
• You have to wrap the commands with error checking using their return code. It is much nicer to use in-language error-codes or exceptions. (os.system() does not let you parse stdout/stderr)
• You have to deal with quoting variables with spaces yourself (or escaping them)
• Python has already done the work for you by supplying the libraries!

Look up glob, for shell-like pattern matching (globbing), and shutil, as others have already mentioned. Otherwise, everything you need is already in the standard libraries.

import glob
import shutil

for extfile in glob.glob('*.ext'):
    shutil.move(extfile,dest)  

In addition, os.system() should not be used - take a look at the subprocess module instead.

Answer 2

Check out Python's shutil module. It offers file system operations such as moving files. Between that and the os module, you should have all the tools you need. This is preferable to the bash commands for the reasons others said.