Type Conversion

What You’ll Learn

Sometimes you need to change the type of a variable. You’ll learn how to cast (convert) data from one type to another.

Basic Casting Functions

Python uses functions to cast values:

• int() - constructs an integer number from an integer literal, a float literal, or a string literal.
• float() - constructs a float number from an integer literal, a float literal, or a string literal.
• str() - constructs a string from a wide variety of data types, including strings, integer literals and float literals.

Examples

To Integer

x = int(1)     # x will be 1
y = int(2.8)   # y will be 2 (decimals are removed)
z = int("3")   # z will be 3

To Float

x = float(1)     # x will be 1.0
y = float(2.8)   # y will be 2.8
z = float("3")   # z will be 3.0
w = float("4.2") # w will be 4.2

To String

x = str("s1")  # x will be 's1'
y = str(2)     # y will be '2'
z = str(3.0)   # z will be '3.0'

Common Mistakes

• Converting invalid strings: Trying to run int("hello") will result in a ValueError, because Python doesn’t know how to turn “hello” into a number.