How to Get File Extension in Python Easily

In Python, you can get a file extension using os.path.splitext() which splits the filename and extension, or by using pathlib.Path.suffix for a modern approach. Both methods return the extension including the dot, like ".txt".

Syntax

There are two common ways to get a file extension in Python:

• Using os.path.splitext(path): This function splits the file path into a tuple (root, ext), where ext is the extension including the dot.
• Using pathlib.Path(path).suffix: This property returns the file extension as a string, including the dot.

python

import os
from pathlib import Path

# Using os.path.splitext
root, ext = os.path.splitext('example.txt')

# Using pathlib.Path
ext_pathlib = Path('example.txt').suffix

Example

This example shows how to get the file extension from a filename using both os.path.splitext and pathlib.Path.suffix. It prints the extension including the dot.

python

import os
from pathlib import Path

filename = 'report.pdf'

# Using os.path.splitext
_, extension1 = os.path.splitext(filename)
print('Extension using os.path.splitext:', extension1)

# Using pathlib.Path
extension2 = Path(filename).suffix
print('Extension using pathlib.Path.suffix:', extension2)

Output

Extension using os.path.splitext: .pdf
Extension using pathlib.Path.suffix: .pdf

Common Pitfalls

Some common mistakes when getting file extensions include:

• Not handling files without extensions, which return an empty string.
• Using string methods like split('.')[-1] which can fail if the filename has multiple dots or no extension.
• For hidden files on Unix systems (like .bashrc), os.path.splitext treats the whole name as extension.

Always prefer os.path.splitext or pathlib.Path.suffix for reliable results.

python

filename = 'archive.tar.gz'

# Wrong way: splitting by dot
ext_wrong = filename.split('.')[-1]
print('Wrong extension:', ext_wrong)  # Outputs 'gz' only

# Right way: using os.path.splitext twice
import os
root, ext = os.path.splitext(filename)
root2, ext2 = os.path.splitext(root)
print('Correct extensions:', ext2 + ext)  # Outputs '.tar.gz'

Output

Wrong extension: gz
Correct extensions: .tar.gz

Quick Reference

Method	Description	Returns
os.path.splitext(path)	Splits path into root and extension	Tuple (root, extension with dot)
pathlib.Path(path).suffix	Gets file extension as string	Extension string with dot
pathlib.Path(path).suffixes	Gets all extensions for multi-dot files	List of extensions with dots

Key Takeaways

Use os.path.splitext() or pathlib.Path.suffix to get file extensions safely.

File extensions include the dot, e.g., '.txt'.

Avoid splitting filenames by dot manually to prevent errors.

For files with multiple extensions, use pathlib.Path.suffixes.

Files without extensions return an empty string as extension.