Bulk Rename Files from the Command Line with Python

Renaming hundreds of files manually is tedious. Here is how to do it with a simple Python script.

The Problem #

You have a folder full of photos and you need to add prefixes, change extensions, or convert case.

Quick Solution #

import os, sys

def rename_files(directory, prefix=""):
    for f in os.listdir(directory):
        fp = os.path.join(directory, f)
        if not os.path.isfile(fp): continue
        name, ext = os.path.splitext(f)
        new_path = os.path.join(directory, prefix + name + ext)
        print(f"{f} -> {os.path.basename(new_path)}")

if __name__ == "__main__":
    rename_files(sys.argv[1], sys.argv[2] if len(sys.argv) > 2 else "")
python renamer.py ./photos vacation_

This adds a prefix to every file in the directory.

Advanced Features #

The full CLI tool (Bulk Renamer Pro) adds:

• Regex find-and-replace
• Case conversion
• Auto-numbering
• Extension filtering
• Recursive scanning
• Safe dry-run mode

Why CLI? #

• Fast: one command, hundreds of files
• Repeatable: same result every time
• Scriptable: chain with other commands

Built with Python 3. No external dependencies.