File I/O

Introduction

Open files with the with statement — it auto-closes the handle even on exceptions. Choose binary mode for non-text data.

Understanding the topic

Core concepts to understand:

• open(path, 'r'|'w'|'a'|'b')
• Always use with for auto-close.
• Text mode handles encoding; binary mode = bytes.
• pathlib.Path for modern path handling.

Syntax reference

Visual flow / code:

from pathlib import Path

# Write
Path("hello.txt").write_text("hi\n", encoding="utf-8")

# Read all
text = Path("hello.txt").read_text(encoding="utf-8")

# Stream line-by-line
with open("big.log", encoding="utf-8") as f:
    for line in f:
        process(line)

# Binary
with open("img.png", "rb") as f:
    data = f.read()

Execution workflow

Real-world use

pathlib replaced os.path in modern Python — type-safe, cross-platform, with chainable methods.

Best practices

• Always use with.
• Always specify encoding=.
• Stream large files line-by-line.

Common mistakes

• Forgetting encoding defaults to platform — broken Unicode on Windows.

Hands-on exercise

Interview preparation — practice these questions:

• Why with open(...)?
• pathlib vs os.path?
• Text vs binary mode?

Summary

In summary: with + encoding + pathlib. Stream — don't slurp.