05_file_io.py

"""
Module 05: File I/O
Learn: open(), read/write, context managers (with), pathlib

In the advanced courses, you'll see:
    content = safe_path(path).read_text()
    fp.parent.mkdir(parents=True, exist_ok=True)
    fp.write_text(content)
"""

# --- Writing a file with open() ---
with open("my_file.txt", "w") as f:
    f.write("Line 1: Hello from Python!\n")
    f.write("Line 2: This is a test file.\n")
print("✅ File written")

# --- Reading a file ---
with open("my_file.txt", "r") as f:
    content = f.read()
print(content)

# --- Reading line by line ---
with open("my_file.txt", "r") as f:
    lines = f.readlines()
    for i, line in enumerate(lines):
        print(f"  Line {i}: {line.strip()}")

# --- pathlib (the modern way — used in Claude Code agent) ---
from pathlib import Path

# Create a path object
workdir = Path(".")
print(f"Working dir: {workdir.resolve()}")

# Write using pathlib
output_path = Path("sample_output.txt")
output_path.write_text("Written with pathlib! 🎉\n")
print(f"Wrote to: {output_path}")

# Read using pathlib
text = output_path.read_text()
print(f"Read back: {text}")

# Useful path operations
some_path = Path("data/reports/summary.csv")
print(f"Name: {some_path.name}")          # summary.csv
print(f"Parent: {some_path.parent}")      # data/reports
print(f"Suffix: {some_path.suffix}")      # .csv

# mkdir with parents (creates all intermediate dirs)
# Path("output/charts").mkdir(parents=True, exist_ok=True)

# --- Cleanup ---
import os
for f in ["sample_output.txt", "my_file.txt"]:
    if os.path.exists(f):
        os.remove(f)
print("🧹 Cleaned up temp files")

# 🎯 Exercise: Write a function that reads a file and returns its line count