File path handling in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the os.path module in Python?

The os.path module helps manage and manipulate file paths in a way that works across different operating systems.

beginner

How do you join directory names and filenames into a full path safely?

Use os.path.join() to combine parts of a path. It adds the right separators for your operating system.

beginner

What does os.path.exists(path) check?

It checks if the file or directory at path actually exists on your computer.

intermediate

Explain the difference between os.path.abspath() and os.path.relpath().

os.path.abspath() gives the full absolute path from the root, while os.path.relpath() gives the path relative to another directory.

intermediate

What is the modern recommended way to handle file paths in Python 3.4+?

Use the pathlib module, which provides an easy and clear object-oriented way to work with file paths.

Which function joins parts of a file path correctly across operating systems?

A os.path.join()

B os.path.split()

C os.path.exists()

D os.path.abspath()

os.path.join() safely combines path parts using the right separator for the OS.

What does os.path.exists('file.txt') return if 'file.txt' is not found?

A Raises an error

B True

C False

D None

os.path.exists() returns False if the file or directory does not exist.

Which module provides an object-oriented way to handle file paths?

A pathlib

B sys

C os.path

D shutil

pathlib offers classes to work with paths in a clear and modern way.

What does os.path.abspath('file.txt') return?

A The relative path to 'file.txt'

B The parent directory path

C The filename only

D The absolute full path to 'file.txt'

os.path.abspath() returns the full absolute path from the root to the file.

Which function splits a path into directory and filename?

A os.path.join()

B os.path.split()

C os.path.exists()

D os.path.relpath()

os.path.split() separates a path into the directory part and the filename.

Describe how to safely combine folder names and filenames into a full path in Python.

Think about how to avoid errors with slashes on Windows vs Linux.

Explain the benefits of using pathlib over os.path for file path handling.

Consider how pathlib uses objects instead of strings.

Practice

1. Which Python module is recommended for safe and easy file path handling?

easy

A. pathlib

B. os.path

C. sys

D. math

Solution

1. Step 1: Identify the module for file paths

   The pathlib module provides an easy and modern way to handle file paths safely.

2. Step 2: Compare with other modules

   While os.path also handles paths, pathlib is recommended for its simplicity and object-oriented approach.

3. Final Answer:

   pathlib -> Option A

4. Quick Check:

   File path handling = pathlib [OK]

Hint: Remember: pathlib is the modern way to handle paths [OK]

Common Mistakes:

• Confusing pathlib with os.path
• Using sys for paths
• Choosing unrelated modules like math

2. Which of the following is the correct way to join paths using pathlib in Python?

easy

A. Path('folder') + 'file.txt'

B. Path('folder') / 'file.txt'

C. Path('folder').join('file.txt')

D. Path('folder').append('file.txt')

Solution

1. Step 1: Understand pathlib path joining

   In pathlib, the slash operator / is overloaded to join paths safely.

2. Step 2: Check each option

   Path('folder') / 'file.txt' uses / correctly. Path('folder') + 'file.txt' uses + which is invalid. The .append() and .join() methods do not exist on Path objects.

3. Final Answer:

   Path('folder') / 'file.txt' -> Option B

4. Quick Check:

   Use slash (/) to join paths [OK]

Hint: Use / operator to join pathlib paths [OK]

Common Mistakes:

• Using + to join paths
• Calling non-existent join or append methods
• Forgetting to import pathlib

3. What will be the output of this code?

from pathlib import Path
p = Path('folder') / 'subfolder' / 'file.txt'
print(p.parts)

medium

A. ('folder/subfolder/file.txt',)

B. ['folder', 'subfolder', 'file.txt']

C. ['folder/subfolder/file.txt']

D. ('folder', 'subfolder', 'file.txt')

Solution

1. Step 1: Understand Path.parts attribute

   The parts attribute returns a tuple of each part of the path as separate strings.

2. Step 2: Analyze the given path

   The path is 'folder/subfolder/file.txt', so parts will be ('folder', 'subfolder', 'file.txt').

3. Final Answer:

   ('folder', 'subfolder', 'file.txt') -> Option D

4. Quick Check:

   Path.parts returns tuple of path parts [OK]

Hint: Path.parts returns a tuple of path components [OK]

Common Mistakes:

• Expecting a list instead of tuple
• Getting full path as one string
• Confusing parts with name or stem

4. What is wrong with this code snippet?

from pathlib import Path
p = Path('folder') + 'file.txt'
print(p)

medium

A. Using + operator to join paths causes TypeError

B. Missing import statement for os module

C. Path object cannot be printed directly

D. The path string should use backslashes instead of forward slashes

Solution

1. Step 1: Check path joining method

   The code uses + operator to join a Path object and a string, which is not supported and raises a TypeError.

2. Step 2: Verify other options

   Import is correct, Path objects can be printed, and forward slashes are valid on most systems.

3. Final Answer:

   Using + operator to join paths causes TypeError -> Option A

4. Quick Check:

   Use /, not +, to join pathlib paths [OK]

Hint: Never use + to join pathlib paths; use / instead [OK]

Common Mistakes:

• Using + operator for path joining
• Thinking Path can't be printed
• Confusing path separators

5. You want to check if a file named data.csv exists inside a folder reports before reading it. Which code correctly does this using pathlib?

hard

A. p = Path('reports') + 'data.csv'
if p.is_file():
print('File found')

B. p = 'reports/data.csv'
if os.path.exists(p):
print('File found')

C. p = Path('reports') / 'data.csv'
if p.exists():
print('File found')

D. p = Path('reports/data.csv')
if p.is_dir():
print('File found')

Solution

1. Step 1: Create path using pathlib and join correctly

   p = Path('reports') / 'data.csv' if p.exists(): print('File found') uses Path('reports') / 'data.csv' which correctly joins folder and file.

2. Step 2: Check if file exists

   p = Path('reports') / 'data.csv' if p.exists(): print('File found') uses p.exists() to check if the file exists before reading, which is correct.

3. Final Answer:

   p = Path('reports') / 'data.csv'\nif p.exists():\n print('File found') -> Option C

4. Quick Check:

   Use pathlib with / and exists() to check files [OK]

Hint: Use Path(...) / filename and exists() to check files [OK]

Common Mistakes:

• Using + to join paths
• Using os.path without import
• Checking is_dir() instead of exists() or is_file()