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Python Fundamentals
Variables and Data Types in Python
What are Variables?
Variables are used to store data that can be used and manipulated in a program.
A variable is created when you assign a value to it using the = operator.
Example:
Variable Naming Rules
Variable names can contain letters, numbers, and underscores. Variable names must start with a letter or underscore. Variable names are case-sensitive. Avoid using Python keywords as variable names (e.g., print , if , else ).
Best Practices
Use descriptive names that reflect the purpose of the variable. Use lowercase letters for variable names. Separate words using underscores for readability (e.g., first_name , total_amount ).
name = "Alice" age = 25 height = 5.
Data Types in Python
Python supports several built-in data types:
Integers ( int ): Whole numbers (e.g., 10 , -5 ). Floats ( float ): Decimal numbers (e.g., 3.14 , -0.001 ). Strings ( str ): Text data enclosed in quotes (e.g., "Hello" , 'Python' ). Booleans ( bool ): Represents True or False. Lists: Ordered, mutable collections (e.g., [1, 2, 3] ). Tuples: Ordered, immutable collections (e.g., (1, 2, 3) ). Sets: Unordered collections of unique elements (e.g., {1, 2, 3} ). Dictionaries: Key-value pairs (e.g., {"name": "Alice", "age": 25} ).
Checking Data Types
Use the type() function to check the data type of a variable.
Typecasting in Python
What is Typecasting?
Typecasting is the process of converting one data type to another. Python provides built-in functions for typecasting: int() : Converts to integer. float() : Converts to float. str() : Converts to string. bool() : Converts to boolean.
print(type(10)) # Output: <class 'int'> print(type("Hello")) # Output: <class 'str'>
Comments, Escape Sequences & Print Statement
Comments
Comments are used to explain code and are ignored by the Python interpreter.
Single-line comments start with #.
Multi-line comments are enclosed in ''' or """.
Escape Sequences
Escape sequences are used to include special characters in strings.
Common escape sequences:
\n : Newline \t : Tab \ : Backslash " : Double quote ' : Single quote
Example:
Print Statement
The print() function is used to display output.
This is a single-line comment
''' This is a multi-line comment '''
print("Hello\nWorld!") print("This is a tab\tcharacter.")
You can use sep and end parameters to customize the output.
Operators in Python
Types of Operators
Arithmetic Operators:
- (Addition), - (Subtraction), * (Multiplication), / (Division), % (Modulus), ** (Exponentiation), // (Floor Division).
Example:
Comparison Operators:
== (Equal), != (Not Equal), > (Greater Than), < (Less Than), >= (Greater Than or Equal), <= (Less Than or Equal).
Example:
Logical Operators:
and , or , not.
Example:
print("Hello", "World", sep=", ", end="!\n")
print(10 + 5) # Output: 15 print(10 ** 2) # Output: 100
print(10 > 5) # Output: True print(10 == 5) # Output: False
print(True and False) # Output: False print(True or False) # Output: True print(not True) # Output: False
