DevMastery
Python
Beginner

Python Programming Fundamentals

30 min read

Start your Python journey with this comprehensive guide to programming fundamentals. Learn syntax, data types, functions, and build your first Python programs.

What You'll Learn

Python syntax and basic structure
Variables and data types
Control flow (if/else, loops)
Functions and parameters
Lists and dictionaries
File handling basics

Introduction to Python

Python is a high-level, interpreted programming language known for its simplicity and readability. Created by Guido van Rossum in 1991, Python has become one of the most popular programming languages in the world.

Why Learn Python?

  • Easy to Learn: Simple, readable syntax that's perfect for beginners
  • Versatile: Used for web development, data science, AI, automation, and more
  • Large Community: Extensive libraries and active community support
  • High Demand: One of the most in-demand programming skills in the job market

Getting Started

Before we start coding, you'll need to install Python on your computer. Visit python.org and download the latest version.

Your First Python Program

print("Hello, World!")
print("Welcome to Python programming!")

Save this code in a file called hello.py and run it with:

python hello.py

Variables and Data Types

Variables in Python are used to store data. You don't need to declare the type explicitly - Python figures it out automatically.

# Numbers
age = 25
height = 5.9
temperature = -10

# Strings
name = "Alice"
message = 'Hello, Python!'
paragraph = """This is a
multi-line string"""

# Boolean
is_student = True
is_working = False

# Lists
fruits = ["apple", "banana", "orange"]
numbers = [1, 2, 3, 4, 5]

# Dictionaries
person = {
    "name": "Bob",
    "age": 30,
    "city": "New York"
}

Working with Variables

# Variable operations
x = 10
y = 3

print(x + y)    # Addition: 13
print(x - y)    # Subtraction: 7
print(x * y)    # Multiplication: 30
print(x / y)    # Division: 3.333...
print(x // y)   # Floor division: 3
print(x % y)    # Modulus: 1
print(x ** y)   # Exponentiation: 1000

# String operations
first_name = "John"
last_name = "Doe"
full_name = first_name + " " + last_name
print(full_name)  # John Doe

# String formatting
age = 25
message = f"I am {age} years old"
print(message)  # I am 25 years old

Control Flow

Control flow statements let you control the execution of your program based on conditions.

If Statements

age = 18

if age >= 18:
    print("You are an adult")
elif age >= 13:
    print("You are a teenager")
else:
    print("You are a child")

# Multiple conditions
temperature = 25
weather = "sunny"

if temperature > 20 and weather == "sunny":
    print("Perfect day for a picnic!")
elif temperature > 20 or weather == "cloudy":
    print("Good day to go outside")
else:
    print("Maybe stay inside today")

Loops

# For loops
fruits = ["apple", "banana", "orange"]

for fruit in fruits:
    print(f"I like {fruit}")

# Range function
for i in range(5):
    print(f"Number: {i}")

for i in range(1, 6):
    print(f"Count: {i}")

# While loops
count = 0
while count < 5:
    print(f"Count is {count}")
    count += 1

# Loop with break and continue
for i in range(10):
    if i == 3:
        continue  # Skip 3
    if i == 7:
        break     # Stop at 7
    print(i)

Functions

Functions help you organize your code into reusable blocks. They make your programs more modular and easier to maintain.

# Basic function
def greet():
    print("Hello, World!")

greet()  # Call the function

# Function with parameters
def greet_person(name):
    print(f"Hello, {name}!")

greet_person("Alice")

# Function with return value
def add_numbers(a, b):
    return a + b

result = add_numbers(5, 3)
print(result)  # 8

# Function with default parameters
def introduce(name, age=25):
    print(f"Hi, I'm {name} and I'm {age} years old")

introduce("Bob")        # Uses default age
introduce("Alice", 30)  # Uses provided age

# Function with multiple return values
def get_name_age():
    return "John", 28

name, age = get_name_age()
print(f"Name: {name}, Age: {age}")

Working with Lists

Lists are one of the most useful data types in Python. They can store multiple items and are very flexible.

# Creating and modifying lists
shopping_list = ["milk", "bread", "eggs"]

# Adding items
shopping_list.append("butter")
shopping_list.insert(1, "cheese")

print(shopping_list)  # ['milk', 'cheese', 'bread', 'eggs', 'butter']

# Accessing items
first_item = shopping_list[0]
last_item = shopping_list[-1]

# Slicing
first_three = shopping_list[:3]
last_two = shopping_list[-2:]

# List methods
numbers = [3, 1, 4, 1, 5, 9, 2, 6]
numbers.sort()          # Sort in place
print(numbers)          # [1, 1, 2, 3, 4, 5, 6, 9]

numbers.reverse()       # Reverse in place
print(numbers)          # [9, 6, 5, 4, 3, 2, 1, 1]

# List comprehensions
squares = [x**2 for x in range(1, 6)]
print(squares)  # [1, 4, 9, 16, 25]

even_numbers = [x for x in range(1, 11) if x % 2 == 0]
print(even_numbers)  # [2, 4, 6, 8, 10]

Dictionaries

Dictionaries store data in key-value pairs, making them perfect for representing structured information.

# Creating dictionaries
student = {
    "name": "Alice",
    "age": 20,
    "major": "Computer Science",
    "gpa": 3.8
}

# Accessing values
print(student["name"])        # Alice
print(student.get("age"))     # 20
print(student.get("phone", "Not provided"))  # Not provided

# Modifying dictionaries
student["age"] = 21           # Update existing key
student["phone"] = "555-1234" # Add new key

# Dictionary methods
print(student.keys())         # dict_keys(['name', 'age', 'major', 'gpa', 'phone'])
print(student.values())       # dict_values(['Alice', 21, 'Computer Science', 3.8, '555-1234'])

# Looping through dictionaries
for key, value in student.items():
    print(f"{key}: {value}")

# Dictionary comprehension
squares_dict = {x: x**2 for x in range(1, 6)}
print(squares_dict)  # {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}

Practical Example: Grade Calculator

Let's put everything together with a practical example - a grade calculator program.

def calculate_grade(scores):
    """Calculate the average grade and letter grade"""
    if not scores:
        return 0, "No grades"
    
    average = sum(scores) / len(scores)
    
    if average >= 90:
        letter = "A"
    elif average >= 80:
        letter = "B"
    elif average >= 70:
        letter = "C"
    elif average >= 60:
        letter = "D"
    else:
        letter = "F"
    
    return average, letter

def main():
    """Main program function"""
    print("Grade Calculator")
    print("-" * 20)
    
    # Get student information
    student_name = input("Enter student name: ")
    
    # Get grades
    grades = []
    while True:
        grade_input = input("Enter a grade (or 'done' to finish): ")
        
        if grade_input.lower() == 'done':
            break
        
        try:
            grade = float(grade_input)
            if 0 <= grade <= 100:
                grades.append(grade)
            else:
                print("Please enter a grade between 0 and 100")
        except ValueError:
            print("Please enter a valid number")
    
    # Calculate and display results
    if grades:
        average, letter = calculate_grade(grades)
        
        print(f"
Results for {student_name}:")
        print(f"Grades: {grades}")
        print(f"Average: {average:.2f}")
        print(f"Letter Grade: {letter}")
    else:
        print("No grades entered.")

# Run the program
if __name__ == "__main__":
    main()

Next Steps

Congratulations! You've learned the fundamentals of Python programming. Here are some areas to explore next:

  • Object-Oriented Programming (Classes and Objects)
  • File handling and working with external data
  • Error handling with try/except
  • Working with modules and packages
  • Web development with Flask or Django
  • Data analysis with pandas and numpy

🐍 Practice Tip

The best way to learn Python is by writing code every day. Try building small projects like a calculator, password generator, or simple games to reinforce these concepts.

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