Getting started · Lesson 4 of 25

Type conversion and input

int, float and str, and why input always returns text.

7 minutes3 games

int("42"), float("3.5"), str(99) and bool(0) convert between types. It matters with input(): it reads what the user types and always returns text, even when they type a number.

Python

age = input("How old are you? ")   # the user types 20
print(age + 1)        # TypeError: can only concatenate str to str
print(int(age) + 1)   # 21

Python

print(int("42") + 8)
print(float("2.5") * 2)
print("Score: " + str(95))
print(int(3.99))            # cuts the decimals: 3
print(bool(""), bool("0"), bool(0), bool([]))

try:
    int("12px")
except ValueError as e:
    print("ValueError:", e)

falsy values =

False[0]

0[1]

0.0[2]

""[3]

[][4]

{}[5]

None[6]

These count as False in conditions; everything else is True.

What's the output?

print(int("7") + int("3"))
print("7" + "3")

What will this code print?

Spot the bug

One line raises a TypeError. Which?

Exercise

Both values arrive as text. Print their sum as a number (30).

Expected output: 30

Python

a = "12"
b = "18"

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Python

Getting started · Lesson 4 of 25

Type conversion and input

int, float and str, and why input always returns text.

7 minutes3 games

int("42"), float("3.5"), str(99) and bool(0) convert between types. It matters with input(): it reads what the user types and always returns text, even when they type a number.

Python

age = input("How old are you? ")   # the user types 20
print(age + 1)        # TypeError: can only concatenate str to str
print(int(age) + 1)   # 21

Python

print(int("42") + 8)
print(float("2.5") * 2)
print("Score: " + str(95))
print(int(3.99))            # cuts the decimals: 3
print(bool(""), bool("0"), bool(0), bool([]))

try:
    int("12px")
except ValueError as e:
    print("ValueError:", e)

falsy values =

False[0]

0[1]

0.0[2]

""[3]

[][4]

{}[5]

None[6]

These count as False in conditions; everything else is True.

What's the output?

print(int("7") + int("3"))
print("7" + "3")

What will this code print?

Spot the bug

One line raises a TypeError. Which?

Exercise

Both values arrive as text. Print their sum as a number (30).

Expected output: 30

Python

a = "12"
b = "18"

Learn more from

Played 0 of 3 games