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String case methods

🧠 Predict the output Topic: strings Difficulty: easy Free

What this problem practises

Python strings are immutable sequences. "Fixing" a string always produces a new one, so the return value has to be captured; slicing rules apply, and every method — upper(), strip(), split(), join() — behaves differently from the in-place mutation you might be picturing.

This is an output-prediction problem: read the snippet carefully and write down exactly what it prints before anything runs. These questions are interview staples because they test whether you know the language rules, or merely recognise their syntax.

Difficulty: easy — the fix or the trick is normally a single line, and a careful read should be enough.

The challenge

The code runs in PyDebug’s in-browser compiler. Open the problem, run the snippet, watch the exact error or output, and keep iterating until it is right. Signed-in solves count toward XP and your daily streak.

The snippet

The interactive editor pre-fills exactly this code — read it, then submit your prediction:

text = "Hello World"
print(text.lower())
print(text.upper())
print(text.title())

Understand the rule

This PyDebug exercise focuses on string case methods. It is a small reproducible Python debugging task: identify the input and expected state, then predict each statement before changing code. When output differs, inspect types, boundaries, mutation, and control flow instead of guessing.

How to trace it

Read the prompt and write the expected output for string case methods.
Run the code mentally, recording values after each loop or function call.
Compare actual and expected states and locate the first divergence.
Make the smallest fix, then test a normal and a boundary case.

Common wrong fixes

Changing several lines at once and hiding the original cause.
Checking only the happy path and missing zero, empty, or boundary input.
Confusing printed representation with the stored value.

Rule to remember

Treat string case methods as a focused experiment. A reliable solution explains the output, handles its edge case, and can be verified with a small test in the browser editor.

Solve it in the interactive editor →

🔮 Learning path: Output Prediction

Problem 4 of 18 in this path. Work them in order — each one builds on the rule before it.

← String multiplication in a loop Next in path: String startswith and endswith →

Keep going

Output-prediction strategies — how to predict tricky snippets without running them.
Browse every strings problem in this topic.
Common Python errors and what they actually mean, plus the Python glossary for any term used on this page.