Variables

In computer science a variable is a named storage location in memory that can hold a value (data). The value stored in a variable can be changed or accessed by the program during its execution.

In Python, variables are created dynamically once a value is assigned to them. This makes Python a dynamically typed language, which means that the data type of a variable is inferred from the value assigned to it. So, you do not need to declare a variable before using it, as in statically typed languages.

The ability to create variables dynamically and infer their data type makes Python code more concise and easier to read. However, it also requires careful attention to variable naming and assignment to avoid unexpected behavior.

In Python = (assignment operator) is used to set a value to some variable, the portion on the left of the operator is a variable name and the portion on the right is a value to assign to a variable.

Variable assignment in Python

number_of_students = 10
greeting = "hello"
pi = 3.14

Variable assignment in Java

int number_of_students = 10;
String greeting = "hello";
double pi = 3.14;

Naming

In Python there are several rules that describe how to name your variables. Some of these are requirements and cannot be ignored, others are rather recommended than required and can be omitted. For now note, that a variable name cannot:

a language keyword (like pass, def or class)
start with a number (e.g. 123, 1_something)
contain special operators in it (+, -, = etc.)
contain white spaces

Also here are some general recommendation on naming anything:

do not use built-in functions as a variable name (e.g. len = 42)
keep names meaningful (x = 10 vs number_of_student = 100)