Character indexing, slices and formatted output. Learn through short examples, practical tasks and targeted questions.
Strings are sequences of characters, so indexing and slicing work in much the same way as with lists. Formatted strings can combine text with variable values for readable output. Experiment with a short word and label its character positions.
Watch out: String indexes start at zero. Slices exclude the ending position, which can surprise students when counting characters.
Character indexing, slices and formatted output. Study the code and predict what it does before running it. Change a value or string and observe how the output changes.
word = "computer"
print(word[0])
print(word[0:3])
score = 87
print(f"Score: {score}%")Ask for a word, then print its first and last characters and its length. Handle an empty word.
Plan your inputs, processing and outputs. Write the code in Mu, IDLE or PyCharm; test at least three cases.
word = input("Word: ")
if word:
print(word[0], word[-1], len(word))
else:
print("No word supplied")Identify the problem and explain how to fix it before revealing the answer.
word = "hello"
print(word[5])word = "hello"
print(word[4])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 →
Predict the effect of slicing before running it; the end index is excluded. Remember that a number typed via input() is still text until converted.
Check: The substring "com": indexes 0, 1 and 2 are included.