Variables in Python

Lecture 10:- Variables in Python

In Python, variables are used to store and represent data in memory. Unlike many other programming languages, Python is dynamically typed, which means you don't need to declare the type of a variable explicitly. Instead, the type is determined automatically based on the value assigned to the variable. Here's how you declare and use variables in Python:

1. Variable Declaration and Assignment: To create a variable, you simply choose a name for it and use the assignment operator (=) to assign a value to it. The general syntax is:

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variable_name = value

Example:

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# Integer variable age = 25 # String variable name = "John Doe" # Float variable salary = 2500.50

1. Variable Naming Rules:
   • Variable names must start with a letter (a-z, A-Z) or an underscore (_).
   • The subsequent characters can be letters, underscores, and digits (0-9).
   • Variable names are case-sensitive, so name, Name, and NAME are treated as different variables.
2. Data Types: As mentioned earlier, Python automatically determines the data type of a variable based on the value assigned to it. Common data types include:
   • Integers (int): Whole numbers, e.g., 42, -15, 0.
   • Floating-Point Numbers (float): Numbers with decimal points, e.g., 3.14, -0.5.
   • Strings (str): Sequences of characters enclosed in single or double quotes, e.g., "hello", 'Python'.
   • Boolean (bool): Represents either True or False.
3. Variable Reassignment: You can change the value of a variable after its initial assignment.

Example:

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age = 25 print(age)  # Output: 25 age = 30  # Reassigning the value print(age)  # Output: 30

1. Multiple Assignment: Python allows you to assign multiple variables in a single line.

Example:

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x, y, z = 10, 20, 30

1. Type Function: You can use the type() function to determine the data type of a variable.

Example:

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x = 42 print(type(x))  # Output: <class 'int'> y = "hello" print(type(y))  # Output: <class 'str'>

Remember that Python variables are dynamically typed, so you can reassign a variable to a value of a different type at any point in your program. This flexibility can be advantageous but also requires careful consideration to avoid unintended behavior.