Python int

Summary: in this tutorial, you’ll learn how to use Python int() to convert a number or a string to an integer.

Introduction to the Python int() constructor #

The int() accepts a string or a number and converts it to an integer. Here’s the int() constructor:

int(x, base=10)

Note that int() is a constructor of the built-in int class. It is not a function. When you call the int(), you create a new integer object.

If x is a string, it should contain a number and is optionally preceded by an optional sign like a minus (-) or plus (+).

If x is a floating point number, the int() returns the integer value of that number.

If x is an object, the int() delegates to the x.__int()__ method. If the object x does not have the __int__() method, the int() will use the __index__() method.

The x argument is optional. If you omit it, the int() will return 0

The base specifies the base for the integer. It defaults to 10.

Python int() examples #

Let’s take some examples of using Python int().

1) Using the int() to convert a string to an integer #

The following example uses the int() to convert strings to integers:

number = int('100')
print(number)  # ? 100

number = int('-90')
print(number)  # ? -90

number = int(' -20\n')
print(number)  # ? -20Code language: Python (python)

2) Using the int() to convert floating point numbers to integers #

The following example uses the int() to convert floating point numbers to integers:

number = int(10.0)
print(number)  # ? 10
number = int(9.99)
print(number)  # ? 9
number = int(5.01)
print(number)  # ? 5Code language: Python (python)

3) Using the Python int() to convert an object to an integer #

The following example illustrates how to use int() to convert an object to an integer:

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __int__(self):
        return int(self.age)


person = Person('John Doe', 22)
print(int(person))  # ? 22
Code language: Python (python)

Output:

22

How it works.

First, define a class Person that has two attributes name and age. The __int__() method returns the integer of the age:

class Product:
    def __init__(self, name, price):
        self.name = name
        self.price = price

    def __int__(self):
        return int(self.price)Code language: Python (python)

Second, create a new instance of the Person and convert it to an integer:

person = Person('John Doe', 22)
print(int(person))  # ? 22Code language: Python (python)

Summary #

• Use Python int() to convert a string or a number to an integer.