The World of Python Programming

Extract Filenames in Python with os.path.basename()

File & Directory Operations
目次

1. What is os.path.basename()?

Python’s os.path.basename() is a function that extracts the file name portion from a specified file path. For example, given a path like “/home/user/documents/file.txt”, os.path.basename() returns “file.txt”. This function is useful in many situations as a cross-platform file operation tool that works across different operating systems.

Overview of os.path.basename()

os.path.basename() is a function in the os module that extracts the last component of a file path (usually the file name). This feature is useful when you want to use the full path but extract only the file name.

Basic usage example

import os

file_path = "/home/user/documents/report.pdf"
file_name = os.path.basename(file_path)
print(file_name)  # Output: report.pdf
This code extracts the file name “report.pdf” from the specified file path. It is used in many situations by everyone from Python beginners to professionals.

2. How to use os.path.basename()

From here, we’ll explain how to use os.path.basename() in practice and go over common usage patterns.

How to get the filename from a file path

If you pass a full path to os.path.basename(), it returns the filename at the end of the path. Since it returns the filename including the extension, you can display it as-is or use it in other processing.

Sample code

import os

file_path = "/home/user/documents/report.pdf"
file_name = os.path.basename(file_path)
print(file_name)  # Output: report.pdf

How to get a directory name from a directory path

If you pass a directory path (rather than a file path) to os.path.basename(), it returns the final element—the directory name. In the example below, “/home/user/documents/” returns “documents”.

Sample code

import os

dir_path = "/home/user/documents/"
directory_name = os.path.basename(dir_path)
print(directory_name)  # Output: documents

Getting a filename including its extension

os.path.basename() returns the filename including its extension. This makes it simple and practical, since you don’t have to check whether an extension exists before getting the filename.

Sample code

import os

file_path = "/path/to/data/file.csv"
file_name_with_extension = os.path.basename(file_path)
print(file_name_with_extension)  # Output: file.csv
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3. Understanding the differences between os.path.basename() and other related functions

os.pathThe module contains several other useful functions for path manipulation besides basename(). Below, we’ll compare with the commonly used os.path.dirname(), os.path.split(), os.path.splitext().

Difference from os.path.dirname()

  • os.path.dirname() retrieves the directory path, whereas os.path.basename() retrieves the file name.

Difference from os.path.split()

  • os.path.split() can return both the directory path and the file name at the same time.

Combining with os.path.splitext()

  • Using os.path.splitext(), you can easily remove the extension from a file name.

4. Make getting filenames easier with pathlib

Since Python 3.4, the pathlib module for file path operations has been standardized. It is more intuitive than os.path and is particularly useful for projects that prioritize readability.

How to use pathlib.Path.name

from pathlib import Path

file_path = Path("/home/user/documents/report.pdf")
print(file_path.name)  # Output: report.pdf
With pathlib.Path.name, you can easily obtain filenames and perform the same operations as basename() in an object-oriented way.
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5. Real-world Examples

Let’s look at the examples below to see how os.path.basename() is used in real projects.

Renaming Files

import os

directory = "/path/to/files"
new_prefix = "new_file"

for index, filename in enumerate(os.listdir(directory)):
    old_file = os.path.join(directory, filename)
    if os.path.isfile(old_file):
        new_file_name = f"{new_prefix}_{index}{os.path.splitext(filename)[1]}"
        new_file = os.path.join(directory, new_file_name)
        os.rename(old_file, new_file)

6. Precautions and Best Practices

When using os.path.basename(), be mindful of OS-specific path separator differences and of using it together with pathlib. Pay attention to the following precautions.
  1. Use os.path.join() and pathlib.Path() for cross-platform compatibility
  2. Verify file existence with os.path.exists() or os.path.isfile()

7. Summary

os.path.basename() is a very handy function for getting the filename from a file path in Python. This article covered the basic usage of basename() as well as related functions and how it differs from pathlib.
  • Getting filenames to cross-platform compatibility, you should now understand how this can be helpful in many practical scenarios.
  • Next steps: consider exploring other os.path functions or using pathlib — they can make file operations even more convenient.
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