Files and Exception Handling

What you will learn

Read and write text files safely.
Understand common file modes.
Use with open(...) so files close reliably.
Catch specific exceptions without hiding programming mistakes.

The code from this chapter

Type these programs yourself. The predictions below are the exercises; the explanations are in the book.

11.1 Writing a Text File

TPRM Lab 11.1: Write and Read

Type this into a file, predict the output, then run it.

Python

with open("notes.txt", "w", encoding="utf-8") as file:
    file.write("First note\n")
    file.write("Second note\n")

with open("notes.txt", "r", encoding="utf-8") as file:
    contents = file.read()

print(contents)

11.2 Expected Errors

TPRM Lab 11.2: Handle Numeric Input

Type this into a file, predict the output, then run it.

Python

while True:
    try:
        age = int(input("Age: "))
        break
    except ValueError:
        print("Please enter a whole number.")

print("Recorded age:", age)