Intro to Python

What is Python?

Python is a high-level, interpreted programming language known for its readability and versatility. It’s used in web development, data science, automation, AI/ML, and more.

Hello World

Python

print("Hello, World!")

Output

Variables and Types

Python is dynamically typed — no need to declare types.

Python

name = "Neil" # str age = 25 # int height = 5.9 # float is_dev = True # bool skills = ["Python", "JS"] # list print(name, age, height, is_dev, skills) print(type(name))

Output

Strings

Python

greeting = "Hello" name = "Neil" # f-strings (Python 3.6+) print(f"{greeting}, {name}!") # Common methods print("hello".upper()) print(" hello ".strip()) print("hello world".split()) print(len("hello"))

Output

Lists

Python

fruits = ["apple", "banana", "cherry"] fruits.append("mango") fruits.insert(1, "orange") fruits.remove("banana") fruits.pop() print("Fruits:", fruits) # Slicing print("First:", fruits[0]) print("Last:", fruits[-1]) # List comprehension squares = [x**2 for x in range(5)] print("Squares:", squares)

Output

Dictionaries

Python

person = { "name": "Neil", "role": "Lead Engineer", "languages": ["Python", "JS"] } print(person["name"]) print(person.get("age", 0)) person["age"] = 25 del person["role"] for key, value in person.items(): print(f"{key}: {value}")

Output

Conditionals

Python

age = 25 if age >= 18: print("Adult") elif age >= 13: print("Teenager") else: print("Child")

Output

Loops

Python

# For loop for fruit in ["apple", "banana", "cherry"]: print(fruit) # Range for i in range(5): print(i, end=" ") print() # Enumerate (index + value) for i, fruit in enumerate(["apple", "banana"]): print(f"{i}: {fruit}")

Output

Functions

Python

def greet(name, greeting="Hello"): return f"{greeting}, {name}!" print(greet("Neil")) print(greet("Neil", "Hey")) # Lambda (anonymous function) double = lambda x: x * 2 print(double(5))

Output

Classes

Python

class Dog: def __init__(self, name, breed): self.name = name self.breed = breed def bark(self): return f"{self.name} says woof!" dog = Dog("Max", "Labrador") print(dog.bark())

Output

Error Handling

Python

try: result = 10 / 0 except ZeroDivisionError: print("Can't divide by zero") except Exception as e: print(f"Something went wrong: {e}") finally: print("This always runs")

Output

File I/O

# Write
with open("notes.txt", "w") as f:
    f.write("Hello from Python")
 
# Read
with open("notes.txt", "r") as f:
    content = f.read()
    print(content)

Modules and Imports

import os
from datetime import datetime
from collections import Counter
 
# Standard library examples
print(os.getcwd())                  # current directory
print(datetime.now())               # current time
print(Counter("banana"))            # Counter({'a': 3, 'n': 2, 'b': 1})

Useful Built-ins

Python

print("len:", len([1, 2, 3])) print("max:", max(1, 5, 3)) print("min:", min(1, 5, 3)) print("sum:", sum([1, 2, 3])) print("sorted:", sorted([3, 1, 2])) print("map:", list(map(str, [1, 2, 3]))) print("filter:", list(filter(lambda x: x > 2, [1, 2, 3, 4]))) print("zip:", list(zip([1, 2], ["a", "b"])))

Output

Next Steps

• Setting Up Python — Get Python installed on your machine
• Setting Up Python with uv — Modern tooling with uv