1.5. Python Data Types

Variables can store different types of data which are used to do different things.

Table 1.3 Python Data Types

Data type	Class	Description
Integer	int	Integer values, e.g., -1, 0, 1, 99
Float	float	Floating point values (decimals), e.g., 1.5, 2.718, 3.1415927
Complex	complex	Complex numbers, e.g., 1 + 2j (note the use of j for the imaginary number)
Boolean	bool	Boolean values, e.g., True or False
String	str	Character string, e.g., "hello world"
List	list	A list of elements, e.g., [1, 1.5, "hello", 1 + 2j]

Python automatically use the appropriate data type for the value being assigned to a variable. The data type can be determined using the type() command.

type(variable)

Enter the following commands into the console.

In [30]: type(-1)
Out[30]: int

In [31]: type(1.5)
Out[31]: float

In [32]: type(1 + 2j)
Out[32]: complex

In [33]: type(True)
Out[33]: bool

In [34]: type("Hello")
Out[34]: str

In [35]: type([1, 1.5, "hello", 1 + 2j])
Out[35]: list

1.5.1. Casting data types

We can change the data type for a variable using casting with the following functions

• int() - returns an integer number from an input of a floating point number or string

• float() - returns a floating point number from an input of an integer or string

• str() - returns a string from a range of data types.

Lets try casting between different data types. Enter the following commands into the console.

In [36]: int(1.23)
Out[36]: 1

In [37]: int("123")
Out[37]: 123

In [38]: float(123)
Out[38]: 123.0

In [39]: float("123")
Out[39]: 123.0

In [40]: str(123)
Out[40]: '123'

In [41]: str(1.23)
Out[41]: '1.23'

In [42]: str(1 + 2j)
Out[42]: '(1+2j)'