Python · Lesson 1.5

Types and converting

Check what kind of value you have, and turn text into numbers (and back).

1Every value has a type

type() tells you what kind of value something is. The four basic types are int, float, str (text) and bool (True or False).

print(type(42))
print(type(3.14))
print(type("42"))
print(type(True))

Python

Practice

Print the type of each value below, one per line.

a = 7
b = "7"
c = 7.0
# Print type(a), type(b), type(c)

Python

Data often arrives as text, and "10" + "5" joins text instead of adding. Convert with int() or float() before doing maths.

a = "10"
b = "5"
print(a + b)
print(int(a) + int(b))

Python

Practice

The two values came from a file as text. Convert them and print their sum: 27.5.

units = "20"
extra = "7.5"
# Convert and print the sum

Python

int() fails on text like "1,200" or " 42 " with spaces. Remove the extra characters first with .replace() and .strip().

raw = " 1,200 "
clean = raw.strip().replace(",", "")
print(int(clean) * 2)

Python

Practice

Turn "$3,450" into the number 3450, then print it times 2.

raw = "$3,450"
# Clean, convert, print times 2

Python

str() turns a number into text, and int() on a float cuts off the decimals rather than rounding.

score = 87
print("Score: " + str(score))
print(int(9.99), round(9.99))

Python

Practice

Print int(price) and then round(price) on separate lines, to see the difference.

price = 4.7
# Two prints

Python

Quick check

What does print("3" * 2) show?