Renaming file names with Python

A few days ago I faced a problem in one of my folders with images. They had a name with a date and some random digits. What I needed was to name the files according to their order, for example, ‘File_nr_1’, ‘File_nr_2’, and so on.

In this short post, I would like to show how I solved this (very easy) task.

First, let’s create a directory with a mockup file. This example directory will consist of empty text files with randomly generated names. I used Bash script to do so.

#!/bin/bash
count=50

for i in $(seq -w 1 $count)
do
    touch "Doc-"$RANDOM.txt
done

Simple enough. Now we have 50 files in our ./example directory. These files have names like ‘Doc-15189.txt’. In Python, if we want to work with files, directories, etc., we can use a built-in os module. We are going to get the directory name, take all files inside as a list, and loop through them to manipulate them.

import os

entries = os.listdir('./example')

for index, name in enumerate(entries):
    current_name = name
    new_name = f"File_nr_{index}"
    if name.endswith('.txt'): # I want to manipulate only files with this extension
        os.rename(current_name, new_name)

This should work, but after running this script we will notice, that our files were removed from its directory and moved one folder up. That’s because we used an absolute path for source files, but a relative path for the destination of the files.

Here’s the fixed and working version:

import os

entries = os.listdir('./example')

for index, name in enumerate(entries):
    current_name = name
    _, ext = os.path.splitext(current_name)
    if name.endswith('.txt'):
        os.rename(os.path.join(file_path, current_name), os.path.join(file_path, str(index) + ext))

This line _, ext = os.path.splitext(current_name) might be a little confusing. The splitext method returns two values. In this case, we want only the second value to be assigned and meaningful for us. So the underscore sign is just a way to assign a value that we want to use later.

This simple scripts can be found in this repository.