Working with strings

What you'll learn

Cut out single letters and pieces of text
Change text with upper(), lower() and replace()
Count letters with a loop

Strings are chains of characters

A piece of text (in Python it’s called a string, type str) is a chain of single characters. Almost everything you learned about lists works here too:

name = "Python"
print(len(name))
print(name[0])
print(name[-1])

Cutting out pieces (slicing)

With [start:end] you cut out a piece. The character at position end is not included any more:

word = "chocolate"
print(word[0:5])
print(word[5:])
print(word[::-1])

Notation	Meaning
`word[0:5]`	characters 0 to 4
`word[5:]`	from character 5 to the end
`word[:3]`	the first 3 characters
`word[::-1]`	everything backwards

Changing text

Strings have many built-in methods. You call them with a dot. The original text stays unchanged – you get a new text back:

sentence = "I like maths."
print(sentence.upper())
print(sentence.lower())
print(sentence.replace("maths", "coding"))
print(sentence.split(" "))
print(sentence)

split() breaks a text into a list. That’s great when someone types several words at once.

Character by character

With for you go through every letter one by one. Here we count how often an “e” appears:

text = "The elephant eats"
count = 0

for char in text.lower():
    if char == "e":
        count = count + 1

print(f"There are {count} e's.")

Tip: There’s also a shortcut for exactly this: text.lower().count("e"). But it’s good to know how it works with a loop.

Quick check

Before you start the task: what does this program print? Type your guess – then Python works it out.

word = "Python"
print(word[0], word[-1], word[1:3])

Your task

Your turn

Ask for a word with input(). Then print three lines, for example for “Robot”: Backwards: toboR, Capitals: ROBOT and Vowels: 2. Count the vowels a, e, i, o and u – no matter whether they are upper or lower case.

word = input("Enter a word: ")

# Your output:

Something to think about
word[::-1] gives you the text backwards.
Which command helps?
Go through every letter with for and check with in "aeiou" whether it's a vowel.
The capital A isn't counted. Turn the word into lower case with lower() first.

Gap code – fill in the ___

                        word = input("Enter a word: ")

print(___)
print(___)

vowels = ___
for letter in ___:
    if ___:
        vowels = ___
print(___)

Solve it without hints to earn a ⭐ on your progress page.

Show solution

Try it yourself first – mistakes teach you the most. Here is one possible solution:

word = input("Enter a word: ")

print(f"Backwards: {word[::-1]}")
print(f"Capitals: {word.upper()}")

vowels = 0
for letter in word.lower():
    if letter in "aeiou":
        vowels = vowels + 1
print(f"Vowels: {vowels}")

Practise more in the training roomEndless new tasks on this topic – with XP and streaks.