Strings & Text Processing — Lesson 3: Clean messy text
New skill: strip, lower, replace
Previously learned: Units 01–06
Why this matters
Searching and tagging work better when extra spaces and inconsistent capitalization are removed.
Step 1 — Explore working Python
Read the program below. Before running it, write down the result you expect.
tag = ' Coding Club '
print(tag.strip())
print(tag.strip().lower())
print(tag.strip().lower().replace(' ', '-'))
Step 2 — Trace the code
.strip()removes leading and trailing spaces..lower()makes letter case consistent..replace(' ', '-')changes internal spaces into hyphens. Apply the operations in order.
Step 3 — Check your understanding
What does ' Game Design '.strip().lower() produce? What remains between the words?
Step 4 — Watch for this mistake
.strip() does not remove spaces between words, and string methods return new strings.
Practice: Clean messy text
Complete normalize_tag(tag) to remove surrounding whitespace, lowercase letters, and replace every internal space with a hyphen.
Function contract: normalize_tag(tag)
Starter file: main.py
Work in the editor, using Run to explore and Check to compare against the published examples. Your submitted code, not the public check, determines the recorded score.
Hint 1 — Start
Begin with `.strip()`.Hint 2 — Build
Chain `.lower()` after removing outside spaces.Hint 3 — Test
Use `.replace(' ', '-')` for internal spaces.Reflect
In 3–5 sentences, explain the algorithm you chose, one test case you predicted, and how you would detect an incorrect answer.
Optional reading
For another perspective on this skill, see How to Think Like a Computer Scientist (interactive textbook). This Playground lesson, worked example, and exercise are original; no textbook passages were reproduced.