Writing, reading and with-open blocks. Learn through short examples, practical tasks and targeted questions.
Text files let a program retain simple data between runs. Opening a file with with closes it automatically at the end of the block. Try writing a few lines, reading them back and checking whether extra newline characters affect the output.
Watch out: Opening a file in write mode replaces its previous contents. Use append mode when earlier lines must be preserved.
Writing, reading and with-open blocks. Study the code and predict what it does before running it. Change a value or string and observe how the output changes.
with open("notes.txt", "w", encoding="utf-8") as file:
file.write("Revise loops\n")
with open("notes.txt", "r", encoding="utf-8") as file:
print(file.read())Create a program that writes three revision targets to a local text file, then reads and prints them.
Plan your inputs, processing and outputs. Write the code in Mu, IDLE or PyCharm; test at least three cases.
targets = ["Practise loops", "Revise lists", "Test functions"]
with open("targets.txt", "w", encoding="utf-8") as file:
for target in targets:
file.write(target + "\n")
with open("targets.txt", "r", encoding="utf-8") as file:
print(file.read())Identify the problem and explain how to fix it before revealing the answer.
with open("notes.txt", "r") as f:
f.write("Hi")with open("notes.txt", "w", encoding="utf-8") as f:
f.write("Hi")Compare the two snippets. Identify the changed line, run the corrected version and explain the effect.
Extension: Improve your solution to deal with unexpected input, add a second feature or display results more clearly.
Reflect: What was the hardest part? What would you test if someone else used your program?
Want extra practice? Try interactive Python tracing and debugging questions →
Test file code using a known small file before trying larger datasets. Explain why with open(...) is usually safer than leaving a file open, and handle the possibility that the requested file is missing.
Check: Python raises FileNotFoundError.