Sometimes you need your program to save data so it's still there next time you run it. That's where file handling comes in!

📁 Why Use Files?

• Data persists — doesn't disappear when the program ends
• You can share data between programs
• You can process large amounts of data at once

✍️ Writing to a File

Syntax:

file = open("filename.txt", "w")
file.write("content")
file.close()

Better — using with (auto-closes):

with open("scores.txt", "w") as file:
    file.write("Alice: 85\n")
    file.write("Bob: 92\n")
    file.write("Charlie: 78\n")
# File automatically closed ✅

📖 Reading from a File

Read entire file:

with open("scores.txt", "r") as file:
    content = file.read()
    print(content)

Read line by line:

with open("scores.txt", "r") as file:
    for line in file:
        print(f"Line: {line.strip()}")

➕ Appending to a File

with open("scores.txt", "a") as file:
    file.write("Diana: 95\n")

🎯 Exam-Style Example: Score Tracker

# Save scores to file
def save_scores(scores, filename):
    with open(filename, "w") as f:
        for score in scores:
            f.write(str(score) + "\n")
    print(f"Saved {len(scores)} scores ✅")

# Load scores from file
def load_scores(filename):
    scores = []
    with open(filename, "r") as f:
        for line in f:
            scores.append(int(line.strip()))
    return scores

# Test it
scores = [85, 92, 78, 90, 88]
save_scores(scores, "my_scores.txt")

loaded = load_scores("my_scores.txt")
print(f"Loaded: {loaded}")
print(f"Average: {sum(loaded)/len(loaded):.1f}")