Numeric Data Types

1.4. Numeric Data Types#

Python supports various data types, which we will introduce as we encounter them. Understanding data types is crucial because each value in Python is associated with a specific data type, and the behavior of values when they are combined is determined by their data types.

To determine the data type of a value, you can use the type() function.

type(2)

int

type(3.14)

float

1.4.1. Int and Float#

Values such as 4 and -7 have the data type int (short for integer). Values like 2.5 and -17.0 belong to the data type float (short for floating point). The value 7j is an instance of the complex data type.

  • int stores whole numbers, whether positive or negative, with unlimited range.

  • float stores numbers with decimals, both positive and negative.

With respect to numeric data types, you should know some rules:

  1. An expression involving two int operands results in an int:

1 + 2

3

type(1 + 2)

int

  1. An expression involving two float operands results in a float:

1.0 + 2.0

3.0

type(1.0 + 2.0)

float

  1. When an expression involves an int and a float as operands, resulting in a mixed data type, Python automatically converts the int to a float. This is why the following two expressions yield the same data type.

17.0 - 10

7.0

type(17.0 - 10)

float

17 - 10.0

7.0

type(17 - 10.0)

float

  1. You can omit 0 after the decimal point, for instance, 10., but this practice is generally considered poor style.

10.

10.0

1.4.1.1. Differences between int and float#

  • float occupies a fixed amount of space, while int takes up a variable amount of space.

  • int values are stored as bignum data type behind the scenes.

import sys
sys.getsizeof(2.0)
Out[3]: 24
sys.getsizeof(2**30)
Out[4]: 32
sys.getsizeof(2**130)
Out[6]: 44

  • Both int and float can store both positive and negative numbers.

  • The type() function is used to determine the data type.

  • float can only represent approximations of real numbers due to the finite amount of memory available in computers.

    • 2/3 vs 1/3

2 / 3

0.6666666666666666

5 / 3

1.6666666666666667

  • If you do not need fraction values, use int.

Contents