Working with operating system paths in Python - Mini Project: Build & Apply

Working with operating system paths

📖 Scenario: Imagine you are organizing files on your computer. You want to work with file paths to check where files are stored and create new paths easily.

🎯 Goal: You will create a program that uses Python's os.path module to join folder names and filenames into full paths, and then display the full paths.

📋 What You'll Learn

Use the os.path module

Create variables for folder names and filenames

Join folder names and filenames into full paths

Print the full paths

💡 Why This Matters

🌍 Real World

Working with file paths is important when you organize files, read or save data, and manage folders on your computer.

💼 Career

Many programming jobs require handling file paths to work with files, such as in data analysis, web development, and automation.

1

Create folder and file name variables

Create a variable called folder and set it to the string 'Documents'. Then create a variable called filename and set it to the string 'notes.txt'.

Python

# Create variables folder and filename with exact values
# Your code here

Hint

Use simple assignment like folder = 'Documents'.

2

Import os.path and create a full path variable

Import the os.path module. Then create a variable called full_path that joins folder and filename using os.path.join().

Python

folder = 'Documents'
filename = 'notes.txt'
# Import os.path and join folder and filename into full_path
# Your code here

Hint

Use import os.path and then os.path.join(folder, filename).

3

Create another file path with a subfolder

Create a variable called subfolder and set it to the string 'Work'. Then create a variable called work_file that joins folder, subfolder, and filename using os.path.join().

Python

import os.path

folder = 'Documents'
filename = 'notes.txt'
full_path = os.path.join(folder, filename)
# Create subfolder variable and join folder, subfolder, filename into work_file
# Your code here

Hint

Use subfolder = 'Work' and join three parts with os.path.join().

4

Print the full paths

Print the variables full_path and work_file each on its own line using two print() statements.

Python

import os.path

folder = 'Documents'
filename = 'notes.txt'
full_path = os.path.join(folder, filename)

subfolder = 'Work'
work_file = os.path.join(folder, subfolder, filename)
# Print full_path and work_file
# Your code here

Hint

Use print(full_path) and print(work_file) to show the paths.

Practice

1. Which function is used to safely combine folder and file names into a full path in Python?

easy

A. os.path.join()

B. os.path.exists()

C. os.path.basename()

D. os.path.dirname()

Solution

1. Step 1: Understand purpose of os.path.join()

   It combines parts of a path into one full path, handling separators correctly.

2. Step 2: Compare with other functions

   os.path.exists() checks if a path exists, basename() gets file name, dirname() gets folder name.

3. Final Answer:

   os.path.join() -> Option A

4. Quick Check:

   Combine paths = os.path.join() [OK]

Hint: Use os.path.join() to build paths safely [OK]

Common Mistakes:

• Confusing join() with exists()
• Using basename() to join paths
• Using dirname() to combine paths

2. Which of the following is the correct syntax to get the folder name from a path stored in variable path?

easy

A. os.path.basename(path)

B. os.path.dirname(path)

C. os.path.join(path)

D. os.path.exists(path)

Solution

1. Step 1: Identify function to get folder name

   os.path.dirname(path) returns the directory part of the path.

2. Step 2: Check other options

   basename() returns file name, join() combines paths, exists() checks path existence.

3. Final Answer:

   os.path.dirname(path) -> Option B

4. Quick Check:

   Folder name = os.path.dirname(path) [OK]

Hint: Use os.path.dirname() to get folder name from path [OK]

Common Mistakes:

• Using basename() to get folder
• Calling join() with one argument
• Confusing exists() with dirname()

3. What will be the output of this code?

import os
path = os.path.join('folder', 'subfolder', 'file.txt')
print(os.path.basename(path))

medium

A. folder

B. subfolder

C. file.txt

D. folder/subfolder/file.txt

Solution

1. Step 1: Understand os.path.join()

   It creates 'folder/subfolder/file.txt' (with correct separator).

2. Step 2: Understand os.path.basename()

   It returns the last part of the path, which is the file name 'file.txt'.

3. Final Answer:

   file.txt -> Option C

4. Quick Check:

   basename() returns file name [OK]

Hint: basename() returns last part (file) of path [OK]

Common Mistakes:

• Expecting folder name instead of file
• Confusing join() output with basename()
• Printing full path instead of basename

4. What is wrong with this code snippet?

import os
path = os.path.join('folder', 'file.txt')
if os.path.exists:
    print('Path exists')

medium

A. os.path.exists is used without parentheses

B. os.path.join() cannot join two parts

C. print statement is missing parentheses

D. Variable path is not defined

Solution

1. Step 1: Check usage of os.path.exists

   It is a function and must be called with parentheses and argument: os.path.exists(path).

2. Step 2: Verify other parts

   join() usage is correct, print() has parentheses, path is defined.

3. Final Answer:

   os.path.exists is used without parentheses -> Option A

4. Quick Check:

   Call exists() with parentheses [OK]

Hint: Call os.path.exists() with path argument [OK]

Common Mistakes:

• Forgetting () after exists
• Passing no argument to exists()
• Misusing join() function

5. You want to check if a file named data.csv exists inside a folder reports located in the user's home directory. Which code correctly builds the path and checks existence?

hard

A. os.path.exists(os.path.join(os.getcwd(), 'reports', 'data.csv'))

B. os.path.exists(os.path.join('reports', 'data.csv'))

C. os.path.exists('~/reports/data.csv')

D. os.path.exists(os.path.join(os.path.expanduser('~'), 'reports', 'data.csv'))

Solution

1. Step 1: Get user's home directory

   Use os.path.expanduser('~') to get the home folder path.

2. Step 2: Join home, reports, and file name

   Use os.path.join() to combine home path, 'reports', and 'data.csv'.

3. Step 3: Check if the full path exists

   Pass the full joined path to os.path.exists() to check existence.

4. Final Answer:

   os.path.exists(os.path.join(os.path.expanduser('~'), 'reports', 'data.csv')) -> Option D

5. Quick Check:

   Expand user + join + exists = os.path.exists(os.path.join(os.path.expanduser('~'), 'reports', 'data.csv')) [OK]

Hint: Use expanduser('~') to get home folder before joining [OK]

Common Mistakes:

• Using relative path without home folder
• Using literal '~/...' without expanduser
• Using current working directory instead of home