Python Programming - Class 3

Introduction

• Third class session covering Python basics.
• Encouraged student participation for feedback and questions about the previous class.
• Recap of the last session's content.

Recap of Last Class

Python Overview

• Python is an interpreted language, not a compiled language.
  • Code is executed line by line.
• Example:

  print("Hello, World!")
  print("End of code")
  

Jupyter Notebook Tips

• Use Shift + Enter to run code and move to the next cell.
• Indentation matters in Python for the code to run correctly.
• Example of a function with indentation:

  def my_function():
      print("Hello, World!")
  

Variables

• Variables are essential in Python for storing objects.
• Variables can be thought of as labels for containers.
• Example:

  name = "John"
  age = 30
  

• Use id() to check the memory location of a variable.
• Example:

  a = "name"
  print(id(a))
  b = "name"
  print(id(b)) # Same as id(a) because they contain the same object.
  

Data Types

• Integers (whole numbers)

  number = 2
  print(type(number)) # <class 'int'>
  

• Float (decimal numbers)

  variable = 2.5
  print(type(variable)) # <class 'float'>
  

• String (text)

  name = "John"
  print(type(name)) # <class 'str'>
  

• None (null value)

  variable = None
  print(type(variable)) # <class 'NoneType'>
  

Data Structures

Lists

• Used to store multiple items in a single variable.
• Created using square brackets [].
• Example:

  names = ["Ala", "Max", "Felix"]
  

• Indexing:

  print(names[0]) # Ala
  print(names[-1]) # Felix
  

• Slicing:

  print(names[0:2]) # ['Ala', 'Max']
  

Dictionaries

• Key-value pairs, created using curly braces {}.
• Example:

  student = {
      "name": "John",
      "email": "john@example.com",
      "age": 21
  }
  

• Accessing dictionary values via keys:

  print(student["name"]) # John
  

• Dictionaries can also contain lists:

  students = {
      "names": ["John", "Jane"],
      "ages": [21, 22]
  }
  

Sets

• Unordered collection of unique elements.
• Define using curly braces {}.
• Removes duplicate elements:

  my_set = {1, 2, 2, 3}
  print(my_set) # {1, 2, 3}
  

Operators

• Arithmetic operations (addition, subtraction, multiplication, division).
• Floor division: //

  print(10 // 3) # 3
  

• Modulus (remainder): %

  print(10 % 3) # 1
  

• Exponentiation: **

  print(2 ** 3) # 8
  

Today's Topic: Control Flow

If-Else Statements

• Executes a block of code only if a specified condition is true.
• Syntax:

  if condition:
      # execute this code
  elif another_condition:
      # execute this code
  else:
      # execute this code
  

Loops

For Loops

• Used to iterate over a sequence (like a list, tuple, or string).
• Example:

  for i in range(5):
      print(i)
  

• Loops over iterable elements.

While Loops

• Runs as long as a certain condition is true.
• Example:

  i = 0
  while i < 10:
      print(i)
      i += 1
  

• Be cautious to avoid infinite loops; use break to stop the loop if necessary.

Break and Continue

• break to exit the loop.
• continue to skip the current iteration and continue with the next one.
• Example:

  for i in range(10):
      if i == 5:
          break
      print(i)
  

Next Class Topic

• Introduction to Object-Oriented Programming (OOP).
• Further topics: importing modules, NumPy, Pandas for data science.