Three Python 3 Methods for Bulk File Renaming

Large-scale file renaming is a common task, especially when sorting and numbering thousands or millions of files. This article discusses three Python 3 approaches to make file names more descriptive or standardized.

1. Rename to recursively numbered files

import os
path = '/path/to/folder'
files = os.listdir(path)
for i, file in enumerate(sorted(files)):
    ext = os.path.splitext(file)[1]
    os.rename(os.path.join(path, file), os.path.join(path, f'{i+1:04d}{ext}'))

Replace path with the target folder. The script enumerates files in sorted order and renames them using a zero‑padded four‑digit sequence.

2. Rename based on file creation time

import os
import time
path = '/path/to/folder'
files = os.listdir(path)
for file in files:
    file_path = os.path.join(path, file)
    creation_time = os.path.getctime(file_path)
    formatted_time = time.strftime('%Y%m%d_%H%M%S', time.localtime(creation_time))
    new_file_name = f'{formatted_time}{os.path.splitext(file_path)[1]}'
    os.rename(file_path, os.path.join(path, new_file_name))

This script obtains each file’s creation timestamp, formats it as YYYYMMDD_HHMMSS , and renames the file accordingly.

3. Rename using regular expressions

import os
import re
path = '/path/to/folder'
files = os.listdir(path)
pattern = re.compile(r'\d{3,4}')
for file in files:
    file_path = os.path.join(path, file)
    match = re.search(pattern, file)
    if match:
        new_file_name = f'{match.group(0)}{os.path.splitext(file_path)[1]}'
        os.rename(file_path, os.path.join(path, new_file_name))

This method extracts numeric patterns from existing file names with a regex and uses the captured digits as the new name, offering flexibility at the cost of more setup.

Each approach has its own strengths: sequential numbering is simple and sortable, timestamp‑based naming embeds useful metadata, and regex‑based renaming provides the most flexibility for custom patterns.