Unit 7 • Lesson 5

Working with File Paths

Overview

File locations can differ between systems, so it's important to manage paths correctly. This lesson covers using the os and pathlib modules to create, join, and navigate directories safely and consistently, ensuring cross-platform compatibility.

Intermediate 20–25 min

Next: Using the with Statement for File Operations All Units

What You Will Learn in This Lesson

By the end of this lesson, you will know:

Relative vs absolute paths: Understand the difference and when to use each.
Path joining: Use os.path.join() to build paths correctly.
The pathlib module: Learn modern Python's preferred way to handle paths.
Cross-platform compatibility: Write code that works on Windows, Mac, and Linux.
Path operations: Check if files exist, get directory names, and more.

Relative vs Absolute Paths

A file path tells Python where to find a file on your computer. There are two types:

Relative Path

Relative to where your program is running. Starts from the current directory.

"data.txt"
"folder/file.txt"
"../parent.txt"

Absolute Path

Complete path from the root of the file system. Works from anywhere.

"/Users/name/data.txt"
"C:\\Users\\name\\data.txt"
"/home/user/data.txt"

When to Use Each

Use relative paths: When files are in the same project folder
Use absolute paths: When you need to access files in specific system locations

Using `os.path.join()`

The os.path.join() function safely combines path parts, using the correct separator for your operating system.

Joining Paths

import os

# Instead of this (WRONG):
path = "folder" + "/" + "file.txt"  # Only works on Mac/Linux

# Do this (RIGHT):
path = os.path.join("folder", "file.txt")  # Works everywhere!

Why Use os.path.join()?

Windows uses \ (backslash)
Mac/Linux use / (forward slash)
os.path.join() automatically uses the right one!

Multiple Path Parts

import os

path = os.path.join("users", "alice", "documents", "file.txt")
# Result: "users/alice/documents/file.txt" (Mac/Linux)
# Result: "users\\alice\\documents\\file.txt" (Windows)

The `pathlib` Module (Modern Python)

Python 3.4+ introduced pathlib, which provides an object-oriented way to work with paths. It's the recommended modern approach.

Using pathlib.Path

from pathlib import Path

# Create a Path object
file_path = Path("folder") / "file.txt"

# Open the file
with open(file_path, "r") as file:
    content = file.read()

pathlib Benefits

More readable code
Cross-platform by default
Many useful methods built-in
Python's recommended way

pathlib Methods

from pathlib import Path

path = Path("folder/file.txt")

print(path.exists())      # Check if file exists
print(path.name)          # "file.txt"
print(path.parent)        # "folder"
print(path.suffix)        # ".txt"
print(path.stem)          # "file"

Common Path Operations

Both os.path and pathlib provide methods for common path operations:

Operation	os.path	pathlib
Join paths	`os.path.join("a", "b")`	`Path("a") / "b"`
Check if exists	`os.path.exists(path)`	`Path(path).exists()`
Get filename	`os.path.basename(path)`	`Path(path).name`
Get directory	`os.path.dirname(path)`	`Path(path).parent`
Get file extension	`os.path.splitext(path)[1]`	`Path(path).suffix`
Get file stem (name without extension)	`os.path.splitext(path)[0]`	`Path(path).stem`
Check if file	`os.path.isfile(path)`	`Path(path).is_file()`
Check if directory	`os.path.isdir(path)`	`Path(path).is_dir()`

More pathlib Examples

from pathlib import Path

file_path = Path("documents/report.pdf")

# Get different parts
print(file_path.name)        # "report.pdf"
print(file_path.stem)        # "report"
print(file_path.suffix)      # ".pdf"
print(file_path.parent)      # "documents"
print(file_path.parts)       # ("documents", "report.pdf")

# Check properties
print(file_path.exists())    # True/False
print(file_path.is_file())   # True/False
print(file_path.is_dir())    # True/False

# Create new paths
new_path = file_path.parent / "backup" / file_path.name
print(new_path)  # "documents/backup/report.pdf"

pathlib Advantages

pathlib is more intuitive and Pythonic:

Object-oriented approach
More readable code
Method chaining: Path("data").parent / "backup" / "file.txt"
Cross-platform by default
Many convenient methods

Practice: Working with Paths

Try It Yourself

Try using pathlib to work with file paths:

from pathlib import Path

path = Path("folder") / "file.txt"
print(f"Path: {path}")
print(f"Name: {path.name}")
print(f"Parent: {path.parent}")

Click "Run Code" to see your output here

What happened? You created a Path object and accessed its properties. The / operator joins paths automatically.

Summary

In this lesson, you learned:

Relative paths: Relative to current directory - use for project files
Absolute paths: Complete system path - use for system files
os.path.join(): Safe way to join paths (works everywhere)
pathlib: Modern, object-oriented path handling
Cross-platform: Always use these tools instead of hardcoding separators

Remember

Never use hardcoded / or \ in paths. Always use os.path.join() or pathlib for cross-platform compatibility!

End-of-Lesson Exercises

Think about these questions to reinforce what you've learned:

Exercise 1: Path Types

What's the difference between a relative path and an absolute path? When would you use each?

Exercise 2: Cross-Platform

Why is it important to use os.path.join() or pathlib instead of hardcoding path separators?

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