🤝 Context Managers — Automatic File Safety

Learn the `with` statement that automatically closes files, even if errors occur.

🎯 The Problem with Manual Closing

Forgetting to close files wastes resources.

# Manual approach - easy to forget close()
file = open("data.txt", "r")
content = file.read()
file.close()  # What if an error happens before this line?

# If error occurs, file never closes!
file = open("data.txt", "r")
content = file.read()
raise Exception("Oops!")  # File stays open!
file.close()  # Never reached

💡 Solution: Use the `with` Statement

`with` automatically closes files when done, even if errors occur.

# File automatically closes when exiting 'with' block
with open("data.txt", "r") as file:
    content = file.read()
    print(content)

# File is automatically closed here
# No need to call file.close()

🎨 Real-World Example: Safe File Processing

# Process file safely - always closes
with open("users.txt", "r") as file:
    for line in file:
        user = line.strip()
        print(f"Processing: {user}")

# File closed automatically

# Writing with safety
with open("output.txt", "w") as file:
    file.write("Line 1\n")
    file.write("Line 2\n")
    # Data is saved and file closed when exiting

# Multiple files at once
with open("input.txt", "r") as in_file, open("output.txt", "w") as out_file:
    content = in_file.read()
    out_file.write(content.upper())

📊 Comparison: Manual vs With Statement

🔑 Key Takeaways

• ✅ `with` statement automatically closes files

• ✅ Safe even if errors occur inside block

• ✅ No need to explicitly call `close()`

• ✅ Always use `with` for file operations

• ✅ Works with multiple files: `with ... , ... :`

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