Syntax Errors

• Syntax errors occur when the code violates Python's grammar rules.
• Example: Missing a closing parenthesis, incorrect indentation.

Runtime Errors

• Runtime errors occur during the execution of a program, when the code encounters an unexpected situation, such as attempting to divide by zero or accessing a non-existent file.
• Example: ZeroDivisionError, FileNotFoundError

Logical Errors

• Logical errors occur when the program does not produce the expected output, although it runs without errors.
• Example: Using the wrong operator in a calculation, leading to incorrect results.

###Formal and Natural Languages

• Formal languages are precisely defined systems with specific rules for syntax and semantics. They are used in areas like programming, mathematics, and logic.
• Natural languages are languages spoken and written by humans, like English or Spanish. They are more flexible and contextually dependent.

###Comparing Formal Languages

• Formal languages are precise and unambiguous, while natural languages can be ambiguous and open to interpretation.
• Formal languages are machine-readable, while natural languages require human interpretation.
• Formal languages are consistent, adhering to strict rules, while natural languages can be inconsistent in their usage.

Brackets in Python

• Parentheses (): Used to define function calls, tuples, and to control operator precedence.
• Square brackets []: Used to create lists, access elements in lists, and define list comprehensions.
• Curly braces {}: Used to define dictionaries, sets, and blocks of code in loops and conditional statements.

Keywords in Python

• Keywords are reserved words with special meanings in Python. They cannot be used as variable names.
• Examples: if, else, for, while, def, class, import, return, try, except, finally, lambda, global, nonlocal, pass, break, continue, assert, yield, del, True, False, None

Arithmetic Operators

• Addition +: Adds two operands.
• Subtraction -: Subtracts the second operand from the first.
• Multiplication *: Multiplies two operands.
• Division /: Divides the first operand by the second.
• Floor division //: Divides two operands and returns the largest whole number less than or equal to the result.
• Modulus %: Returns the remainder of the division of the first operand by the second.
• Exponentiation **: Raises the first operand to the power of the second.
• Example: 5 + 2 = 7, 10 / 2 = 5, 10 // 3 = 3, 10 % 3 = 1, 2 ** 3 = 8

Bitwise Operators

• Bitwise AND &: Performs a bit-by-bit AND operation on the operands.

• Bitwise OR |: Performs a bit-by-bit OR operation on the operands.

• Bitwise XOR ^: Performs a bit-by-bit exclusive OR operation on the operands.

• Bitwise NOT ~: Inverts the bits of the operand.

• Left shift <<: Shifts the bits of the operand to the left by a specified number of positions.

• Right shift >>: Shifts the bits of the operand to the right by a specified number of positions.

• Example: ```python a = 10 # Binary: 1010 b = 5 # Binary: 0101

  Bitwise AND: 1010 & 0101 = 0000 (Decimal: 0)

  print(a & b)

  Bitwise OR: 1010 | 0101 = 1111 (Decimal: 15)

  print(a | b)

  Bitwise XOR: 1010 ^ 0101 = 1111 (Decimal: 15)

  print(a ^ b)

  Bitwise NOT: ~1010 = 0101 (Decimal: 5)

  print(~a)

  Left shift: 1010 << 2 = 101000 (Decimal: 40)

  print(a << 2)

  Right shift: 1010 >> 2 = 0010 (Decimal: 2)

  print( a >> 2)

Logical Operators

• Logical AND and: Returns True if both operands are True, otherwise False.
• Logical OR or: Returns True if at least one operand is True, otherwise False.
• Logical NOT not: Inverts the logical state of the operand.
• Example: True and False = False, True or False = True, not True = False

Comparison Operators

• Equal to ==: Returns True if both operands are equal, otherwise False.
• Not equal to !=: Returns True if both operands are not equal, otherwise False.
• Greater than >: Returns True if the first operand is greater than the second, otherwise False.
• Less than <: Returns True if the first operand is less than the second, otherwise False.
• Greater than or equal to >=: Returns True if the first operand is greater than or equal to the second, otherwise False.
• Less than or equal to <=: Returns True if the first operand is less than or equal to the second, otherwise False.
• Example: 5 == 5 = True, 5 != 6 = True, 5 > 4 = True, 5 < 6 = True, 5 >= 5 = True, 5 <= 5 = True

Operator Precedence and Associativity

• Operator precedence determines the order in which operators are evaluated in an expression.
• Operator associativity determines how operators of the same precedence are grouped in the absence of parentheses (left-to-right or right-to-left).
• Example: 5 + 2 * 3 = 11 (Multiplication has higher precedence than addition).
  • 5 - 2 - 1 = 2 (Subtraction is left-associative, so operations are performed from left to right).

If-Elif Control Structure

• The if-elif control structure allows for multiple conditions to be checked in sequential order until a condition is met.
• Example:

    grade = int(input("Enter your grade: "))
    if grade >= 90:
        print("Excellent!")
    elif grade >= 80:
        print("Very Good!")
    elif grade >= 70:
        print("Good!")
    else:
        print("Needs improvement!")

Looping Structures

• for loop: Iterates over a sequence, such as a list or string.
• while loop: Executes a block of code repeatedly as long as a condition is True.
• Example:

    # for loop
    fruits = ["apple", "banana", "cherry"]
    for fruit in fruits:
        print(fruit)

    # while loop 
    count = 0
    while count < 5:
        print("Count:", count)
        count += 1 

Conversion Functions

• int(): Converts a value to an integer.
• float(): Converts a value to a floating-point number.
• str(): Converts a value to a string.
• bool(): Converts a value to a Boolean (True or False).
• Example:

    num_str = "10"
    num_int = int(num_str)  # Converts string "10" to integer 10.
    print(type(num_int))  # Output: <class 'int'>

    num_float = float(num_str)  # Converts string "10" to float 10.0.
    print(type(num_float))  # Output: <class 'float'>

    num_bool = bool(num_str)  # Converts string "10" to Boolean True (non-zero values are True).
    print(type(num_bool))  # Output: <class 'bool'>

Defining and Using Functions in Python

• A function is a block of reusable code that performs a specific task.
• Syntax:

    def function_name(parameters):
        # Code to be executed
        return value

• Parameters: Input values passed to the function.
• Return value: The value returned by the function.
• Example:

    def add_numbers(x, y):
        return x + y

    result = add_numbers(5, 3) # Calling the function - 8
    print(result) 

Function Types

• Fruitful functions: Functions that return a value.
• Void functions: Functions that do not return a value, but may perform other tasks.
• Boolean functions: Functions that return a Boolean value (True or False).
• Composite functions: Functions that call other functions within their definition.
• Example:

    # Fruitful Function
    def square(x):
        return x * x

    # Void Function
    def greet(name):
        print(f"Hello, {name}!")

    # Boolean Function
    def is_even(num):
        return num % 2 == 0

    # Composite Function
    def calculate_average(x, y):
        sum = add_numbers(x, y)
        average = sum / 2
        return average

Recursive Functions

• Recursive functions are functions that call themselves within their definition.
• Example:

    def factorial(n):
        if n == 0:
            return 1
        else:
            return n * factorial(n - 1)

    print(factorial(5)) # Output: 120

String Functions

• len(string): Returns the length of a string.
• string.upper(): Converts a string to uppercase.
• string.lower(): Converts a string to lowercase.
• string.strip(): Removes leading and trailing whitespace from a string.
• string.replace(old_string, new_string): Replaces all occurrences of old_string with new_string in a string.
• string.split(separator): Splits a string into a list of substrings separated by the specified separator.
• string.join(separator, iterable): Joins the elements of an iterable (like a list) into a string, separated by the specified separator.
• Example:

    my_string = "  Hello, World!  "
    print(len(my_string))         # Output: 18 (including spaces)
    print(my_string.upper())       # Output:   HELLO, WORLD!  
    print(my_string.lower())       # Output:   hello, world!  
    print(my_string.strip())       # Output: Hello, World!
    print(my_string.replace("Hello", "Hi"))   # Output:   Hi, World!  
    print(my_string.split(","))       # Output: ['  Hello', ' World!  ']
    words = ["apple", "banana", "cherry"]
    print(", ".join(words))   # Output: apple, banana, cherry

Lists and List Functions

• A list is an ordered sequence of elements.
• Creating a list:

    my_list = [1, 2, 3, "apple", "banana"]

• Accessing elements:

    print(my_list[0])  # Output: 1 (first element) 
    print(my_list[-1])  # Output: banana (last element)

• append(element): Adds an element to the end of the list.
• insert(index, element): Inserts an element at a specified index.
• remove(element): Removes the first occurrence of a given element from the list.
• pop(index): Removes and returns the element at the specified index.
• sort(): Sorts the list in ascending order.
• reverse(): Reverses the order of the elements in the list.
• len(list): Returns the length of the list.
• Example:

    my_list = [1, 2, 3]
    my_list.append(4)              # Adds 4 to the end
    my_list.insert(1, 5)            # Inserts 5 at index 1
    my_list.remove(2)             # Removes the first occurrence of 2
    print(my_list.pop(0))         # Removes and returns the element at index 0 (Output: 1)
    my_list.sort()                # Sorts the list ascending order
    my_list.reverse()              # Reverses the order of the elements
    print(len(my_list))             # Output: 3 (Length of the list)

Tuples and Tuple Functions

• A tuple is an ordered, immutable sequence of elements.
• Creating a tuple:

    my_tuple = (1, 2, 3, "apple", "banana") 

• Accessing elements:

    print(my_tuple[0])  # Output: 1 
    print(my_tuple[-1]) # Output: banana

• Tuples have limited functions as they are immutable, hence elements cannot be modified. But, we can use functions like len() to determine the length of a tuple.
• Example:

    my_tuple = (1, 2, 3)
    print(len(my_tuple)) # Output: 3

Differences between Lists and Tuples

• Mutability: Lists are mutable (elements can be changed), while tuples are immutable (elements cannot be changed).
• Use Cases: Lists are used for collections that need to be modified frequently, while tuples are used for collections that should remain unchanged.

Dictionaries and Dictionary Functions

• A dictionary is an unordered collection of key-value pairs.
• Creating a dictionary:

    my_dict = {"name": "Alice", "age": 30, "city": "New York"} 

• Accessing values:

    print(my_dict["name"])  # Output: Alice (accessing value using key)

• keys(): Returns a view object containing the keys of the dictionary.
• values(): Returns a view object containing the values of the dictionary.
• items(): Returns a view object containing key-value pairs as tuples.
• get(key, default): Returns the value associated with the specified key. If the key is not found, it returns the default value.
• update(other_dict): Updates the dictionary with key-value pairs from another dictionary.
• Example

    my_dict = {"name": "Alice", "age": 30, "city": "New York"}

    print(my_dict.keys())   # Output: dict_keys(['name', 'age', 'city'])
    print(my_dict.values())  # Output: dict_values(['Alice', 30, 'New York'])
    print(my_dict.items())   # Output: dict_items([('name', 'Alice'), ('age', 30), ('city', 'New York')])

    print(my_dict.get("name"))     # Output: Alice
    print(my_dict.get("occupation", "Not provided")) # Output: Not provided (key not found)

    my_dict.update({"occupation": "Software Engineer"}) # Updates dictionary with new key-value pair
    print(my_dict)  # Output: {"name": "Alice", "age": 30, "city": "New York", "occupation": "Software Engineer"}

• Note: Dictionary values can be of any data type (integers, strings, lists, etc.).

Reading and Writing to Files

• Opening a file:

    file = open("filename.txt", "mode")

• Modes:
  • "r": Read mode (default)
  • "w": Write mode (overwrites existing file or creates a new one)
  • "a": Append mode (adds new content to the end of the file)
  • "x": Create mode (creates a new file and fails if the file exists)
  • "b": Binary mode (for working with non-text files)
  • "t": Text mode (default)
• Closing a file:

    file.close()

File Read and Write Methods

• read(): Reads the entire content of the file into a string.
• readline(): Reads a single line from the file.
• readlines(): Reads all lines from the file into a list.
• write(text): Writes the specified text to the file.
• Example:

    # Writing to a file
    with open("my_file.txt", "w") as file:
        file.write("This is some text to write to the file.\n")
        file.write("Another line of text.\n")

    # Reading from a file
    with open("my_file.txt", "r") as file:
        content = file.read()
        print(content)

Exception Handling in Python

• An exception is an error that occurs during the execution of a program.
• try-except block: Used to handle exceptions.
• Syntax:

    try:
        # Code that may raise an exception
    except ExceptionType:
        # Code to handle the exception

• Example:

    try:
        num1 = int(input("Enter first number: "))
        num2 = int(input("Enter second number: "))
        result = num1 / num2
        print("Result:", result)
    except ZeroDivisionError:
        print("Error: Cannot divide by zero!")
    except ValueError:
        print("Error: Invalid input. Please enter numbers only.")

Built-in Exceptions

• ZeroDivisionError: Raised when attempting to divide by zero.
• ValueError: Raised when an operation receives an argument of an incorrect type.
• TypeError: Raised when an operation or function is applied to an object of an inappropriate type.
• NameError: Raised when a variable is not defined.
• IndexError: Raised when trying to access an element outside the range of a sequence (like a list or string).
• KeyError: Raised when trying to access a key that does not exist in a dictionary.
• FileNotFoundError: Raised when trying to open a file that does not exist.
• IOError: Raised when an input/output operation fails (like trying to write to a read-only file).
• AttributeError: Raised when trying to access an attribute that does not exist in an object.
• SyntaxError: Raised when the parser encounters invalid syntax.

Metacharacters in Regular Expressions

• Metacharacters are special characters that have special meanings in regular expressions.
• .: Matches any single character except a newline.
• *: Matches 0 or more occurrences of the preceding character.
• +: Matches one or more occurrences of the preceding character.`
• ?: Matches 0 or 1 occurrence of the preceding character.`
• ^: Matches the beginning of the string.`
• $: Matches the end of the string.`
• []: Matches any character within the square brackets.`

Creating classes and objects in Python

• Class: A blueprint for creating objects.
• Object: An instance of a class.
• Syntax:

    class ClassName:
        # Attributes (data members)
        # Methods (functions within the class) 

Inheritance in Python

• Inheritance allows a class to inherit properties and methods from another class (parent class).
• Syntax:

    class ChildClass(ParentClass):
        # ... 

• Example:

    class Animal:
        def __init__(self, name):
            self.name = name

        def speak(self):
            print("Animal sound")

    class Dog(Animal):
        def speak(self):
            print("Bark!")

    my_dog = Dog("Buddy")
    my_dog.speak()  # Output: Bark!

Threads in Python

• Thread: A lightweight unit of execution within a program.
• Creating a thread:

    import threading

    def my_function():
        # Thread's code
        print("Thread running!")

    thread = threading.Thread(target=my_function)
    thread.start()  # Starts the thread

Thread Synchronization

• Synchronization: Ensuring that multiple threads access shared resources in a coordinated manner, preventing race conditions.
• Lock object:

    import threading

    lock = threading.Lock()
    lock.acquire()  # Acquires the lock (making the resource exclusive)
    # Critical section (code that needs synchronized access)
    lock.release()  # Releases the lock

Creating Modules in Python

• Module: A file containing Python code that can be imported and used in other programs.
• Creating a Module:
• Create a Python file (e.g., my_module.py).
• Write functions, classes, and variables in this file.
• Importing a module:

    import my_module

Methods from Math, Random, and Time Modules

• math.sqrt(x): Returns the square root of x.
• math.pow(x, y): Returns x raised to the power of y.
• random.randint(a, b): Returns a random integer between a and b (inclusive).
• random.random(): Returns a random floating-point number between 0.0 and 1.0.
• time.time(): Returns the current time in seconds since the epoch.
• time.sleep(seconds): Pauses the program for the specified number of seconds.
• time.strftime(format): Formats a time object according to the specified format string.

Data Storage in Databases

• Databases store data in a structured and organized manner.
• Relational Database Management System (RDBMS): Organizes data into tables with rows and columns.
• SQL (Structured Query Language): Used to interact with RDBMS, performing operations like creating, reading, updating, and deleting data (CRUD).

Select Queries in Python

• SELECT statement: Used to retrieve data from a database table.
• Syntax:

    SELECT column1, column2, ...
    FROM table_name
    WHERE condition; 

Layout Managers in Python

• Layout managers: Help you organize widgets (graphical elements) within a window.
• pack: Simple layout, arranges widgets in a single row or column.
• grid: Arranges widgets in a 2D grid.
• place: Positions widgets using absolute coordinates.

Tkinter Widgets

• Button: A clickable button.
• Canvas: Used to draw shapes, lines, and images.
• Checkbutton: A checkbox.
• Entry: A text input field.
• Frame: A container for other widgets.
• Label: A text label.
• Listbox: A scrollable list of items.
• Radiobutton: A radio button (select only one option from a group).
• Scale: A slider control.
• Text: A multi-line text area.
• LabelFrame: A framed label with a border.
• tkMessageBox: Displays message boxes.
• Menu: A menu bar with submenus.

Creating Menu Systems in Python

• Creating a menu bar:

    menubar = tk.Menu(root)
    filemenu = tk.Menu(menubar, tearoff=0)
    filemenu.add_command(label="Open", command=open_file)
    filemenu.add_command(label="Save", command=save_file)
    filemenu.add_separator()
    filemenu.add_command(label="Exit", command=root.quit)
    menubar.add_cascade(label="File", menu=filemenu)
    root.config(menu=menubar)

Event Handling in Python

• Event handling: Responding to user actions, like button clicks or mouse movements.
• Binding events to widgets:

    button = tk.Button(root, text="Click me")
    button.bind("<Button-1>", button_clicked) 
    button.pack()