Variables and Data Types in Python

Variables And Data Types

• Variables:
  • A name given to a value
  • Assigned using the assignment operator (=)
  • Can be reassigned
• Data Types:
  • Integer (int): whole numbers, e.g. 1, 2, 3, etc.
  • Float (float): decimal numbers, e.g. 3.14, -0.5, etc.
  • String (str): sequence of characters, e.g. "hello", 'hello', etc.
  • Boolean (bool): true or false values
  • NoneType (None): represents the absence of a value
• Type Conversion:
  • Using built-in functions, e.g. int(), float(), str(), etc.
  • Implicit conversion, e.g. when using operators

Operators And Control Structures

• Arithmetic Operators:
  • Addition: a + b
  • Subtraction: a - b
  • Multiplication: a * b
  • Division: a / b
  • Modulus: a % b
• Comparison Operators:
  • Equal: a == b
  • Not Equal: a != b
  • Greater Than: a > b
  • Less Than: a < b
  • Greater Than or Equal: a >= b
  • Less Than or Equal: a <= b
• Logical Operators:
  • And: a and b
  • Or: a or b
  • Not: not a
• Control Structures:
  • If-Else Statements:
    • If condition: executes if condition is true
    • Else clause: executes if condition is false
  • For Loops:
    • Iterates over a sequence (e.g. list, string)
    • Executes a block of code for each item
  • While Loops:
    • Executes a block of code while a condition is true

Functions And Modules

• Functions:
  • A block of code that can be executed multiple times
  • Defined using the def keyword
  • Can take arguments and return values
• Function Arguments:
  • Positional Arguments: passed in the order they are defined
  • Keyword Arguments: passed using the parameter name
• Modules:
  • A collection of related functions and variables
  • Imported using the import keyword
  • Examples: math, statistics, time, etc.

Lists And Tuples

• Lists:
  • A collection of items that can be changed
  • Defined using square brackets []
  • Items can be added, removed, or modified
• Tuples:
  • A collection of items that cannot be changed
  • Defined using parentheses ()
  • Items cannot be added, removed, or modified
• Indexing and Slicing:
  • Accessing individual items using their index (0-based)
  • Slicing: accessing a subset of items using a range of indices
• List Methods:
  • append(): adds an item to the end of the list
  • insert(): adds an item at a specific position
  • remove(): removes the first occurrence of an item
  • sort(): sorts the list in ascending order

Variables And Data Types

• A variable is a name given to a value, which can be assigned using the assignment operator (=) and reassigned as needed.
• There are five basic data types in programming:
  • Integer (int), which represents whole numbers, such as 1, 2, 3, etc.
  • Float (float), which represents decimal numbers, such as 3.14, -0.5, etc.
  • String (str), which is a sequence of characters, such as "hello", 'hello', etc.
  • Boolean (bool), which can have a value of either true or false.
  • NoneType (None), which represents the absence of a value.

Operators And Control Structures

• Arithmetic Operators are used to perform mathematical operations, including:
  • Addition (a + b)
  • Subtraction (a - b)
  • Multiplication (a * b)
  • Division (a / b)
  • Modulus (a % b)
• Comparison Operators are used to compare values, including:
  • Equal (a == b)
  • Not Equal (a != b)
  • Greater Than (a > b)
  • Less Than (a < b)
  • Greater Than or Equal (a >= b)
  • Less Than or Equal (a <= b)

Data Structures

• Lists:
  • Ordered collections of items, allowing for modification and duplicate values.
  • Indexing starts at 0, making it easy to access specific elements.
  • Example: my_list = [1, 2, 3, 4, 5]
• Tuples:
  • Ordered, immutable collections of items, preventing modification after creation.
  • Like lists, tuples can contain duplicates, but indexing starts at 0.
  • Example: my_tuple = (1, 2, 3, 4, 5)
• Dictionaries:
  • Unordered collections of key-value pairs, allowing for modification.
  • Keys must be unique, preventing duplicates.
  • Example: my_dict = {'name': 'John', 'age': 30}
• Sets:
  • Unordered collections of unique items, allowing for modification.
  • Automatically removes duplicates, ensuring a unique set of items.
  • Example: my_set = {1, 2, 3, 4, 5}

Loops

• For Loop:
  • Used for iterating over sequences (strings, lists, tuples, etc.).
  • The syntax is for variable in iterable:, making it easy to iterate over collections.
  • Example: fruits = ['apple', 'banana', 'cherry']; for fruit in fruits: print(fruit)
• While Loop:
  • Used for iterating as long as a condition is true.
  • The syntax is while condition:, allowing for customized looping.
  • Example: i = 0; while i < 5: print(i); i += 1

Conditional Statements

• If Statement:
  • Used for making decisions based on conditions.
  • The syntax is if condition:, allowing for simple decision-making.
  • Example: x = 5; if x > 10: print('x is greater than 10')
• If-Else Statement:
  • Used for making decisions based on conditions with an alternative option.
  • The syntax is if condition: else:, providing a default response if the condition is false.
  • Example: x = 5; if x > 10: print('x is greater than 10'); else: print('x is less than or equal to 10')