Strings

A string is a piece of text, and Python is flexible about how you write one: you can use single quotes ('hello') or double quotes ("hello") interchangeably — both create the exact same kind of string. It's useful to know both work, especially when your text itself contains a quote character, like 'She said "hi"'. You can join strings together with the + operator, called concatenation — though unlike some languages, Python will not automatically convert a number to text for you with +, so mixing a string and a number this way causes an error.

first = "Py"
second = "thon"
print(first + second)  # PyThon

# print("Score: " + 95)  # this would raise a TypeError

The much more convenient way to build text with variables inside it is an f-string: put an f right before the opening quote, then write any expression inside curly braces {} and Python inserts its value automatically, converting it to text for you.

name = "Ada"
points = 95
print(f"Hello, {name}! Your score is {points}.")

Strings come with useful tools. len(s) returns how many characters are in a string. .upper() and .lower() return a new copy of the string in all uppercase or all lowercase. Slicing, written s[start:end], grabs a piece of the string from index start up to (but not including) index end — and like everything in Python, indexing starts counting at 0.

word = "Python"
print(len(word))       # 6
print(word.upper())    # PYTHON
print(word.lower())    # python
print(word[0:3])       # Pyt

To insert a variable directly into a string without manually converting it, you can write an ____, such as f"Hello, {name}".

What does "Python"[0:3] return?

In Python, "hello" + 5 works fine and automatically converts the number to text.