Sometimes a value is the wrong type for what you need — you have a number stored as text, or you need to combine a number with a string. Python lets you convert between types explicitly.

str() — convert to text

age = 25
message = "I am " + str(age) + " years old"
print(message)

Without str(age), this line would crash — Python won't automatically combine a str and an int with +. Converting age to a string first fixes that.

int() — convert to a whole number

text_number = "42"
real_number = int(text_number)
print(real_number + 8)

int() also truncates (chops off, doesn't round) decimals when converting from a float:

print(int(9.9))
print(int(9.1))

float() — convert to a decimal number

text_price = "19.99"
price = float(text_price)
print(price * 2)

When conversion fails

Not every string can become a number. This will raise an error:

int("hello")

You'll see errors like this throughout your Python career — reading them (they usually tell you exactly what went wrong) is a core skill. We'll cover handling errors properly in Module 6.

Try it yourself

You're given a number as text. Convert it to an int, add 10 to it, then print the result.

Checkpoint

• str(x) converts x to text.
• int(x) converts x to a whole number (truncates floats).
• float(x) converts x to a decimal number.
• Converting an invalid string (like int("hello")) raises an error.