Unit 5: Words, Deeper
Pull text apart and rebuild it.
Unit 5 of 31 in Python for kids. Its 5 lessons are Letter by Letter, Cutting Slices, String Powers, Looping Over Letters and Word Wizard — below is everything each one explains, and a question or two from it to try.
Every sample on this page was run through real Python before it shipped, and prints exactly what it says it prints.
This unit opens with a fortnight’s trial of everything — no card needed — or with a family plan, bought in the iPhone app. The first two units of every track are free for ever. Try it in the app.
🔡 Letter by Letter
Words are rows of letters
You can reach into a word the same way you reach into a list — square brackets and a number. Counting starts at 0, so the first letter is number 0.
Python
word = "code"
print(word[0])
print(word[2])It prints
c d
Counting backwards
A minus number counts from the end. -1 is the last letter — much tidier than working out the length first.
Python
word = "code"
print(word[-1])
print(word[-2])It prints
e d
Try it yourself
What does this print?
Python
word = "python"
print(word[1])How do you get the LAST letter of any word, however long?
- word[0]
- word[1]
- word[-1]
- word[len(word)]
Answer them in the app
🍰 Cutting Slices
Taking a piece
Two numbers with a colon cuts a slice out. It starts at the first number and stops *before* the second — the same rule range uses.
Python
word = "dragon"
print(word[0:3])
print(word[3:6])It prints
dra gon
Leaving a number out
Miss out the first number and it starts at the beginning; miss out the second and it runs to the end.
Python
word = "dragon"
print(word[:3])
print(word[3:])It prints
dra gon
Try it yourself
What does this print?
Python
word = "python"
print(word[1:4])What does this print?
Python
word = "birthday"
print(word[:5])Answer them in the app
✨ String Powers
Words can do things
Strings carry their own little tools, used with a dot after the word. They hand back a new word — the original never changes.
Python
name = "ada"
print(name.upper())
print(name)It prints
ADA ada
Swapping and trimming
replace swaps one bit of text for another. strip removes stray spaces from the ends — invaluable when a person typed the text.
Python
print("I like cats".replace("cats", "dogs"))
print(" hi ".strip())It prints
I like dogs hi
Breaking a sentence up
split chops a sentence into a list of words, cutting wherever it finds a space.
Python
words = "red green blue".split()
print(words)
print(len(words))It prints
['red', 'green', 'blue'] 3
Try it yourself
What does this print?
Python
print("SHOUT".lower())After name = "ada" and name.upper(), what is in name?
- "ADA"
- "ada"
- nothing
- an error
Answer them in the app
🔄 Looping Over Letters
A word is loopable
A for loop walks through a word one letter at a time, exactly as it walks through a list.
Python
for letter in "cat":
print(letter)It prints
c a t
Is it in there?
in asks whether something appears inside a word or a list. It gives back True or False.
Python
print("z" in "pizza")
print("q" in "pizza")It prints
True False
Try it yourself
What does this print?
Python
count = 0
for letter in "banana":
if letter == "a":
count = count + 1
print(count)What does this print?
Python
print("cat" in "concatenate")Answer them in the app
🏆 Word Wizard
Try it yourself
What does this print?
Python
word = "wizard"
print(word[0].upper() + word[1:])What does this print?
Python
print("hello"[::-1])Answer them in the app