Variable in Python#

Python variable is a storage container or to reserve a memory location with a name to store a value or data temporally and then used to refer to that value in your code. Variables are fundamental to any programming language.

  • Variables keep values accessible

  • Variables give values perception

  • Variables make change easy

  • Variables have data types

Variable Declaration#

Python is a dynamically typed language, a variable is created when you first assign a value to it. Variables do not need to be declared with any particular type, and can even be changed after they have been set.

# Assign a string value to a variable
device_name = "Router1"

# Assign an integer value to a variable
device_port = 22

# Assign a boolean value to a variable
is_connected = True

You can get the data type of a variable with the type() function.

ip_addr = "192.168.10.1"
print(type(ip_addr))

<class 'str'>

Assign values to multiple variables in one statement.

vlan_01, vlan_10 = "default", "mgmt"
print(vlan_01, vlan_10)

default mgmt

Assign the same value to multiple variables at once.

host = ip_addr = "192.168.10.1"
print(host, ip_addr)

192.168.10.1 192.168.10.1

If you have a collection of values in a list, tuple etc. Python allows you to extract the values into variables.

ip_addr_list = ["10.10.10.10", "172.16.10.10", "192.168.10.10"]

ip_addr1, ip_addr2, ip_addr3 = ip_addr_list

print(ip_addr1)
print(ip_addr2)
print(ip_addr3)

10.10.10.10
172.16.10.10
192.168.10.10

Assignment statements#

An operator is a symbol that operates on one or more values. Values are assigned to a variable using a special symbol called the assignment operator =. The = operator takes the value to the right of the operator and assigns it to the name on the left.

hostName = "R-01"
print(hostName)

R-01

String variables can be declared either by using single 'R-01' or double quotes "R-01".

hostName = "R-01"
print(hostName)

R-01

hostName = 'R-01'
print(hostName)

R-01

Variable Naming Convention#

Variable names can be as long or as short as you like, but there are a few rules to follow.

  • A variable name must start with a letter or the underscore character.

  • A variable name cannot start with a number.

  • A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ ).

  • keywords are reserved words that cannot be used as variable names or other identifiers.

  • Variable names are case-sensitive.

# Camel Case - Each word, except the first, starts with a capital letter.
myVariableName = "Alex"
# Pascal Case - Each word starts with a capital letter.
MyVariableName = "Alex"
# Snake Case - An underscore character separates each word.
my_variable_name = "Alex"

You may also want to consider using all-caps naming convention for variables that represent constants or configuration values that should not be modified during runtime. For example:

# Define a constant value using all-caps naming convention
MAX_DEVICES = 100

Using all-caps variable names for constants can make it clear that the value should not be modified and helps to distinguish them from regular variables.

Note

As a network engineer, you may want to use variable names that are descriptive and meaningful, such as device_name, device_ip, device_username, and device_password. Using meaningful variable names can make your code more readable and easier to understand for yourself and others who may read your code.