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🐍 Python Programming
A complete guide to Python programming from basics to advanced concepts
1. Variables and Data Types
What is it? Variables store information like a box. Data types tell what kind of information (text, number, etc).
python_basics.py
# Variables store data
name = "Alice" # Text (String)
age = 25 # Whole number (Integer)
height = 5.9 # Decimal number (Float)
is_student = True # True or False (Boolean)
# Print to show output
print(f"Name: {name}")
# Convert between types
num_text = "123"
num = int(num_text) # Convert text to number
2. If Statements (Conditions)
What is it? Conditions let your code make decisions. "If this happens, do that. Otherwise, do something else."
if_statements.py
age = 25
if age >= 18:
print("You are an adult")
elif age >= 13:
print("You are a teenager")
else:
print("You are a child")
# Check multiple conditions
if age >= 18 and has_license:
print("Can drive")
3. Loops (Repeat Code)
What is it? Loops repeat code multiple times. Useful for doing the same thing over and over.
loops.py
# For loop - repeat a set number of times
for i in range(5):
print(i) # Prints: 0, 1, 2, 3, 4
# For loop - go through a list
fruits = ["apple", "banana", "orange"]
for fruit in fruits:
print(fruit)
# While loop - repeat until condition is false
count = 0
while count < 3:
print(count)
count = count + 1
4. Lists (Store Multiple Items)
What is it? A list is like a shopping list - it stores multiple items in order. You can add, remove, or change items.
lists.py
# Create a list
numbers = [1, 2, 3, 4, 5]
# Access items (0 is first)
print(numbers[0]) # Shows: 1
print(numbers[-1]) # Shows: 5 (last item)
# Add and remove
numbers.append(6) # Add 6 to end
numbers.remove(3) # Remove 3 from list
numbers.pop() # Remove last item
# List length
print(len(numbers)) # Shows: 5
# Check if item in list
if 2 in numbers:
print("Found it!")
5. Functions (Reusable Code)
What is it? Functions are blocks of code you can reuse. Instead of writing the same code multiple times, put it in a function and call it.
functions.py
# Define a simple function
def greet(name):
return f"Hello {name}!"
result = greet("Alice")
print(result) # Shows: Hello Alice!
# Function with default value
def add(a, b=0):
return a + b
print(add(5)) # Uses default: 5 + 0 = 5
print(add(5, 3)) # 5 + 3 = 8
# Function that doesn't return anything
def say_hello(name):
print(f"Hello {name}!")
say_hello("Bob")
6. Dictionaries (Key-Value Storage)
What is it? A dictionary stores pairs of information - like a phone book where you look up a name (key) to find a number (value).
dictionaries.py
# Create a dictionary
person = {
"name": "Alice",
"age": 25,
"city": "New York"
}
# Access by key
print(person["name"]) # Shows: Alice
# Add new key-value
person["email"] = "alice@example.com"
# Update value
person["age"] = 26
# Remove key
del person["city"]
# Get all keys
print(person.keys())
7. Classes and Objects
What is it? Classes are blueprints for creating objects. Like a cookie cutter that makes the same shape cookies, a class defines how objects should look and behave.
classes.py
# Define a class
class Dog:
def __init__(self, name, age):
self.name = name
self.age = age
def bark(self):
return f"{self.name} says Woof!"
# Create objects from the class
dog1 = Dog("Buddy", 3)
dog2 = Dog("Max", 5)
# Use the objects
print(dog1.name) # Shows: Buddy
print(dog1.bark()) # Shows: Buddy says Woof!
8. File Handling (Read and Write)
What is it? Working with files lets you save data to your computer and read it back later.
files.py
# Read a file
with open("file.txt", "r") as f:
content = f.read()
print(content)
# Write to a file
with open("output.txt", "w") as f:
f.write("Hello, World!")
# Add to a file (append)
with open("log.txt", "a") as f:
f.write("\nNew message")
9. Error Handling (Try-Except)
What is it? Sometimes code fails (like dividing by zero). Try-Except lets you handle errors gracefully instead of crashing.
error_handling.py
try:
num = int("abc")
result = 10 / 0
except ValueError:
print("That's not a valid number")
except ZeroDivisionError:
print("Can't divide by zero")
except Exception as e:
print(f"Something went wrong: {e}")
else:
print("No errors!")
10. Lambda (Quick Functions)
What is it? Lambda is a way to write small functions quickly without using def. Perfect for simple, one-time operations.
lambda.py
# Lambda function - quick and simple
square = lambda x: x ** 2
print(square(5)) # Shows: 25
# Use with map - apply to all items
numbers = [1, 2, 3, 4, 5]
squared = list(map(lambda x: x**2, numbers))
print(squared) # Shows: [1, 4, 9, 16, 25]
# Use with filter - keep only matching items
even = list(filter(lambda x: x % 2 == 0, numbers))
print(even) # Shows: [2, 4]