Writing & Appending Files

import io

# Write mode ('w') — overwrites!
output = io.StringIO()
output.write("Hello, World!\n")
output.write("Python is awesome!\n")
output.write(f"2 + 3 = {2 + 3}\n")
print("Written content:")
print(output.getvalue())

# Writing multiple lines
output2 = io.StringIO()
lines = ["Line 1\n", "Line 2\n", "Line 3\n"]
output2.writelines(lines)
print(output2.getvalue())

# Real file writing patterns:
# with open("output.txt", "w") as f:
#     f.write("Hello!\n")

# Append mode ('a') — adds to end
# with open("log.txt", "a") as f:
#     f.write("New log entry\n")

# Write with print()
# with open("output.txt", "w") as f:
#     print("Hello!", file=f)

# Practical: generate a report
report = io.StringIO()
data = [("Alice", 85), ("Bob", 92), ("Charlie", 78)]
print("=== Student Report ===", file=report)
for name, score in data:
    grade = "A" if score >= 90 else "B" if score >= 80 else "C"
    print(f"{name}: {score} ({grade})", file=report)
print(f"Average: {sum(s for _, s in data)/len(data):.1f}", file=report)
print(report.getvalue())