Variable in Python

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Mindvault360

• Introduction to Python
• Comments
• Variable in Python
• Python Datatypes
• Python Operators
• Conditional Statements

Variables in Python are used to hold values that can be referenced and changed throughout the program. Here's an overview of Python variables, their kinds, and how they function:

Variable Declaration: 

In Python, the type of a variable is automatically inferred based on its assigned value, eliminating the need for explicit declaration.

Example:

x = 5          # Integer

name = "John"  # String

price = 19.99  # Float

is_active = True  # Boolean

Variable Naming Rules: 

1. Variable names must begin with a letter or underscore (_).
2. Subsequent characters may be letters, numbers, or underscores.
3. Variable names are case-sensitive (for example, name and Name are not the same variable).
4. Python keywords (such as if, while, and for) are not allowed.

Common Variable Types:

 Integer: Whole numbers, positive or negative.

 x = 10

 y = -5

Float: Numbers with a decimal point.

pi = 3.14159

temperature = -5.2

String: A set of characters. It should be enclosed within double quotes

greeting = "Hello, world!"

Boolean: Represents True or False.

is_valid = True

has_error = False

None: This is similar to "null" in other languages

result = None

Multiple Assignments:

Likewise, in other programming languages, in python we can also be able to assign multiple values in a single line.

a, b, c = 1, 2, "apple"

Type Checking:

You can check the type of a variable using the type() function.

x = 5
print(type(x))  # Output: <class 'int'>

Type Casting:

You can convert between types using type casting functions like int(), float(), str() etc.
x = "123"
y = int(x)  # Converts string to integer

Global and Local Variables:

• Global variables are defined outside of functions and are accessible throughout the program.
• Local variables are defined within functions and are accessible only within that function.

x = 10  # Global variable

def my_function():

    x = 5  # Local variable

    print(x)  # 5 (local x is used)

print(x)  # 10 (global x is used)

Changing Global Variables Inside Functions:

To modify a global variable within a function, you need to use the global keyword.

x = 10

def modify_variable():

    global x

    x = 20

modify_variable()

print(x)  # 20

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