Data Types

A data type tells Python what kind of value a variable holds and what operations can be performed on it. Python determines the type automatically based on the value you assign — this is called dynamic typing.

Overview of Core Data Types¶

Type	Example	Description
`int`	`x = 5`	Whole numbers, positive or negative
`float`	`y = 3.14`	Decimal/floating-point numbers
`str`	`s = "hello"`	Text — any characters in quotes
`bool`	`b = True`	Only two values: `True` or `False`
`list`	`l = [1, 2, 3]`	Ordered collection, can be changed
`tuple`	`t = (1, 2, 3)`	Ordered collection, cannot be changed
`dict`	`d = {"key": "val"}`	Key-value pairs for fast lookups
`set`	`s = {1, 2, 3}`	Unordered, only stores unique values
`NoneType`	`x = None`	Represents the absence of a value

Numeric Types¶

x = 5       # int — whole number
y = 3.14    # float — decimal number

String Type¶

Strings store text. You can use single or double quotes — both work the same way:

message = "Hello, Network Engineer!"
device = 'Cisco2960_south'
# Both are valid str types

Boolean Type¶

Booleans can only be True or False (capital first letter required). They are the result of comparisons and are used in conditions:

is_online = True
is_configured = False

Sequence Types¶

my_list  = [1, 2, 3]    # list — ordered and changeable
my_tuple = (1, 2, 3)    # tuple — ordered but cannot be changed
my_range = range(5)     # range — represents a sequence of numbers (0,1,2,3,4)

NoneType¶

None is used to represent "nothing" or "no value". It is commonly used as a default or placeholder:

result = None   # No value yet — will be assigned later

Checking a Variable's Type¶

x = 42
print(type(x))       # <class 'int'>

name = "Router1"
print(type(name))    # <class 'str'>

Explicitly Setting a Type (Type Casting)¶

Sometimes you need to force a value into a specific type. This is called type casting:

variableName = str("This is a string")
variableName = int(42)
variableName = list(("192.168.1.100", "192.168.1.101", "192.168.1.102"))
variableName = tuple(("192.168.1.100", "192.168.1.101", "192.168.1.102"))
variableName = dict(routerName="Cisco5501", ip="10.200.30.254")
variableName = set(("192.168.1.100", "192.168.1.101", "192.168.1.102"))

A common use case is converting a number to a string so you can concatenate it with text:

port_number = 8080
message = "Connecting on port " + str(port_number)