Variables
A variable in Python is a named reference to a value stored in memory. Python uses dynamic typing, meaning you
don’t need to declare a variable’s type—it’s determined at runtime based on the assigned value.
In simple terms, a variable is like a labeled box where you can store different types of information, such as numbers,
words, or lists.
x = 10 # Integer variable
name = "Alice" # String variable
price = 99.99 # Float variable
is_valid = True # Boolean variable
Python automatically assigns the correct data type to each variable based on the assigned value.
Python allows you to assign multiple variables in a single line:
name, age, is_student = "Bob", 30, True
print(name) # Output: Bob
print(age) # Output: 30
print(is_student) # Output: True
Naming Rules for Variables
- Must start with a letter (a-z, A-Z) or underscore (_)
- Cannot start with a number
- Can contain letters, numbers, and underscores
- Case-sensitive (
nameandNameare different variables) - Should not be a Python keyword (e.g.,
class,if,def, etc.)
Constants in Python
Python does not have built-in constant support, but by convention, constants are written in uppercase letters:
PI = 3.14159
GRAVITY = 9.8
By convention, we do not change the values of constants after they are defined.