Variables in Python

Introduction

• Variables are like containers in Python programming, similar to kitchen containers storing different items (e.g., rice, sugar).
• Variables store values in the computer's RAM.

Creating Variables

• Declaration: a = 1
• Printing a variable: print(a)
• When you write a = 1, '1' is stored in memory and 'a' points to that memory address.

Examples

• b = 'Harry': Assign a string to a variable with double quotes.
• Important: Strings should be enclosed in double quotes to avoid errors.
  • Example: Without quotes, print(b) might treat 'b' as a variable pointing to another value.

Variable Types

1. Integers: Whole numbers (e.g., a = 1)
2. Floats: Decimal numbers (e.g., a = 1.1)
3. Strings: Text enclosed in quotes (e.g., b = 'Harry')
4. Booleans: True or False values

Checking Variable Types

• Using type() function: print(type(a)) # Output: <class 'int'> print(type(b)) # Output: <class 'str'>

Different Data Types in Python

1. Numbers
   • Integer: Whole numbers
   • Float: Decimal numbers
   • Complex: Real and Imaginary parts (e.g., a = 2 + 3j)
2. Strings: A sequence of characters (e.g., s = "Hello")
3. Booleans: True or False
4. Sequences
   • Lists: Mutable collection of items (e.g., [1, 2, 'a'])
   • Tuples: Immutable list (e.g., (1, 2, 'a'))
5. Mappings: Dictionaries
   • Key-value pairs (e.g., d = {'name': 'Harry', 'age': 25})

Lists and Tuples

• Lists: Collection of items of different types, mutable.
  • Creation: list = [1, 2, 'a']
  • Can store another list inside it.
• Tuples: Similar to lists but immutable.
  • Creation: tuple = (1, 2, 'a')
  • Can't be changed.

Dictionary

• Collection of key-value pairs.
  • Example: student = {'name': 'Sakshi', 'age': 20, 'can_vote': True}

Variable Concepts and Operations

• Python requires specifying the type of value that a variable can hold to perform operations correctly. a = 1 b = 2 print(a + b) # Output: 3
• Mixing types can cause errors. a = 1 b = 'Harry' print(a + b) # Error, can't add integer and string

Mutable and Immutable Types

• Mutable: Can be changed (e.g., Lists).
• Immutable: Cannot be changed (e.g., Tuples).
• Remember: Mutation means change.

Everything is an Object in Python

• In Python, everything is an object (Integers, strings, etc.).
• Class types indicate what kind of object a variable is.

Conclusion

• Understanding different data types and their behaviors is crucial for efficient programming.
• Python's flexibility with variable types allows for dynamic and complex operations.

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