Introduction to Python Programming

• Python is a high-level, general-purpose programming language.
• Its design philosophy emphasizes code readability with the use of significant indentation.
• Python is dynamically typed and garbage-collected.
• It supports multiple programming paradigms, including structured (particularly procedural), object-oriented, and functional programming.
• Python is often described as a "batteries included" language due to its comprehensive standard library.
• Guido van Rossum created Python and first released it in 1991.
• The Python Software Foundation holds a non-exclusive license to use, modify, and redistribute Python.

Key Features

• Readable and Maintainable Code: Python's syntax emphasizes readability, making it easier to understand and maintain code.
• Multiple Programming Paradigms: Python supports various programming styles, including object-oriented, imperative, and functional programming.
• Cross-Platform Compatibility: Python runs on many different operating systems like Windows, macOS, and Linux.
• Extensive Standard Library: Python has a large collection of built-in modules and functions, reducing the need for external libraries for many tasks.
• Open Source and Community Supported: Python is open-source, meaning it is free to use and distribute, and it has a large and active community contributing to its development.

Variables and Data Types

• Variables: Used to store data values.
  • Variable names are case-sensitive.
  • No explicit declaration is needed; a variable is created when a value is assigned to it.
• Data Types:
  • Integers: Whole numbers (e.g., 1, 100, -5).
  • Floating-Point Numbers: Numbers with a decimal point (e.g., 3.14, 2.0).
  • Strings: Sequences of characters (e.g., "Hello", 'Python').
  • Booleans: Represents True or False.
  • Lists: Ordered collections of items, can contain elements of different types, and are mutable.
  • Tuples: Ordered, immutable collections of items.
  • Dictionaries: Collections of key-value pairs.
  • Sets: Unordered collections of unique elements.

Operators

• Arithmetic Operators:
  • + (addition)
  • - (subtraction)
  • * (multiplication)
  • / (division)
  • // (floor division - integer division)
  • % (modulus - remainder of division)
  • ** (exponentiation)
• Comparison Operators:
  • == (equal to)
  • != (not equal to)
  • > (greater than)
  • < (less than)
  • >= (greater than or equal to)
  • <= (less than or equal to)
• Logical Operators:
  • and (logical AND)
  • or (logical OR)
  • not (logical NOT)
• Assignment Operators:
  • = (assign value)
  • +=, -=, *=, /=, %= (shorthand assignment operators)
• Membership Operators:
  • in (returns True if a sequence with the specified value is present in the object)
  • not in (returns True if a sequence with the specified value is not present in the object)
• Identity Operators:
  • is (returns True if both variables are the same object)
  • is not (returns True if both variables are not the same object)

Control Flow

• Conditional Statements:
  • if: Used to execute a block of code if a condition is true.
  • elif (else if): Tests an additional condition if the previous if condition is false.
  • else: Executes a block of code if all preceding conditions are false.
• Loops:
  • for: Iterates over a sequence (like a list, tuple, or string).
  • while: Executes a block of code as long as a condition is true.
• Loop Control Statements:
  • break: Terminates the loop and transfers control to the next statement after the loop.
  • continue: Skips the rest of the current iteration and continues with the next iteration of the loop.
  • pass: Does nothing; it is a null statement.

Functions

• Definition: A block of organized, reusable code used to perform a single, related action.
• Syntax:
  • Defined using the def keyword.
  • Can accept arguments (parameters) as input.
  • Can return values using the return statement.
• Types of Arguments:
  • Positional Arguments: Passed to a function in the order they are defined.
  • Keyword Arguments: Passed to a function with the name=value syntax.
  • Default Arguments: Arguments that have a default value if not provided in the function call.
  • Variable-Length Arguments: Can accept an arbitrary number of arguments using *args (non-keyword arguments) and **kwargs (keyword arguments).
• Lambda Functions:
  • Anonymous functions defined using the lambda keyword.
  • Limited to a single expression.
  • Often used for short, simple operations.

Data Structures

• Lists:
  • Ordered, mutable collections of items.
  • Defined using square brackets [].
  • Allow duplicate elements.
  • Methods: append(), insert(), remove(), pop(), index(), count(), sort(), reverse().
• Tuples:
  • Ordered, immutable collections of items.
  • Defined using parentheses ().
  • Allow duplicate elements.
  • Methods: count(), index().
• Dictionaries:
  • Unordered collections of key-value pairs.
  • Defined using curly braces {}.
  • Keys must be unique and immutable (e.g., strings, numbers, tuples).
  • Values can be of any data type.
  • Methods: get(), keys(), values(), items(), pop(), update().
• Sets:
  • Unordered collections of unique elements.
  • Defined using curly braces {} or the set() constructor.
  • Do not allow duplicate elements.
  • Methods: add(), remove(), discard(), pop(), union(), intersection(), difference(), symmetric_difference().

Modules

• Modules: Files containing Python code that can be imported and used in other programs.
• Standard Library: A vast collection of modules that come with Python.
• Importing Modules:
  • import module_name: Imports the entire module.
  • from module_name import item_name: Imports a specific item from the module.
  • import module_name as alias: Imports the module with an alias.
• Commonly Used Modules:
  • math: Mathematical functions and constants.
  • datetime: Date and time manipulation.
  • os: Operating system interface.
  • random: Random number generation.
  • json: JSON encoding and decoding.
  • re: Regular expressions operations.

File Handling

• Opening Files:
  • Use the open() function to open a file.
  • Specify the file path and mode (e.g., 'r' for read, 'w' for write, 'a' for append, 'b' for binary).
• Reading Files:
  • read(): Reads the entire file content as a string.
  • readline(): Reads a single line from the file.
  • readlines(): Reads all lines and returns them as a list of strings.
• Writing Files:
  • write(): Writes a string to the file.
  • writelines(): Writes a list of strings to the file.
• Closing Files:
  • Use the close() method to close the file.
  • Using the with statement automatically closes the file after the block is executed.

Object-Oriented Programming (OOP)

• Classes: Blueprints for creating objects.
  • Defined using the class keyword.
  • Contain attributes (data) and methods (functions).
• Objects: Instances of classes.
• Attributes: Variables that store data associated with an object.
• Methods: Functions defined within a class that operate on objects of that class.
• self: A reference to the instance of the class, used to access attributes and methods within the class.
• Constructor (__init__): A special method that is automatically called when an object is created.
• Inheritance: A mechanism where a new class inherits attributes and methods from an existing class (base class or parent class).
• Polymorphism: The ability of an object to take on many forms.
• Encapsulation: Bundling of data and methods that operate on that data within a class, and restricting access to some of the object's components.

Error Handling

• Exceptions: Events that occur during program execution that disrupt the normal flow of instructions.
• Try-Except Blocks:
  • try: Encloses the code that might raise an exception.
  • except: Specifies the code to be executed if a particular exception occurs.
  • else: Specifies the code to be executed if no exception occurs in the try block.
  • finally: Specifies the code to be executed regardless of whether an exception occurs or not.
• Raising Exceptions:
  • Use the raise keyword to manually raise an exception.
• Common Exceptions:
  • TypeError: Occurs when an operation or function is applied to an object of inappropriate type.
  • ValueError: Occurs when a function receives an argument of the correct type but an inappropriate value.
  • IndexError: Occurs when trying to access an index that is out of range.
  • KeyError: Occurs when trying to access a non-existent key in a dictionary.
  • FileNotFoundError: Occurs when trying to open a file that does not exist.

Virtual Environments

• Isolated environments for Python projects.
• Allow you to manage dependencies for different projects separately.
• Created using venv module or tools like virtualenv.
• Activating a virtual environment modifies the PATH so that the project's local packages are used.

List Comprehensions

• A concise way to create lists in Python.
• Consists of an expression followed by a for clause, then zero or more for or if clauses.
• Example: squares = [x**2 for x in range(10)]

Generators

• Functions that return an iterator that produces a sequence of values when iterated over.
• Use the yield keyword to return values one at a time.
• Memory-efficient for large sequences because they generate values on-the-fly.

Decorators

• Functions that modify the behavior of other functions.
• Use the @ syntax to apply a decorator to a function.
• Allow you to add functionality to functions without modifying their original code.

Testing

• Unit Testing: Testing individual components or units of code.
• Testing Frameworks:
  • unittest: Python's built-in testing framework.
  • pytest: A popular third-party testing framework.
• Test Cases: Individual tests that check specific aspects of the code.
• Test Suites: Collections of test cases.

Learn about Python, a versatile high-level programming language known for its readability and comprehensive standard library. Created by Guido van Rossum and first released in 1991, Python supports multiple programming paradigms, making it suitable for various applications.