Python float()

Summary: in this tutorial, you’ll learn how to use Python float() to convert a number or a string to a floating point number.

Introduction to the Python float() #

The float() accepts a string or an number, either an integer or a floating-point number, and converts it to a floating-point number, if possible:

float(x)Code language: Python (python)

If x is a string, it should contain a decimal number. Also, it can have an optional sign like a minus (-) or plus (+).

If x is an integer or a floating point number, the float() returns the same floating point number with the same value. If the value is outside the range of a Python float, the float() will raise an OverflowError.

If x is an object, the float() delegates to the x.__float__() method. If the object x does not have the __float__() method, the float() will use the __index__() method.

The x parameter is optional. If you omit it, the float() will return 0.0.

Python float() examples #

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

1) Using float() to convert a string to a floating point number #

The following example uses the float() to convert strings to floating point numbers:

f = float('+1.99')
print(f)  # ? 1.99

f = float('-5.99')
print(f)  # ? -5.99

f = float('199e-001')
print(f)  # ? 19.9

f = float('+1E3')
print(f)  # ? 1000.0

f = float('-Infinity')
print(f)  # ? -infCode language: Python (python)

2) Using float() to convert an integer to a floating point number #

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

f = float(10)
print(f)  # ? 10.0

f = float(-20)
print(f)  # ? -20.0

f = float(0)
print(f)  # ? 0.0

f = float()
print(f)  # ? 0.0Code language: Python (python)

3) Using the Python float() to convert an object to a floating point number #

The following example illustrates how to convert an object to a floating point number:

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

    def __float__(self):
        return float(self.price)


phone = Product('phone', 999)
print(float(phone))Code language: Python (python)

Output:

999.0Code language: Python (python)

How it works.

First, define a class Product that has two attributes name and price. The __float__() method returns the floating point number of the price:

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

    def __float__(self):
        return float(self.price)Code language: Python (python)

Second, create a new instance of the product and convert it to a floating point number:

phone = Product('phone', 999)
print(float(phone))Code language: Python (python)

Summary #

• Use the Python float() to convert a string or an integer to a floating point number.