Python Core Concepts

🐍 Python Core Concepts: Your Journey Begins!

Imagine Python as your friendly robot assistant. You give it simple instructions, and it does exactly what you ask. Just like teaching a pet new tricks, you’ll teach Python to do amazing things!

🌟 Python Basics: Meeting Your New Friend

Think of Python like a super-smart calculator that can also talk, remember things, and make decisions!

What is Python?

Python is a language that computers understand. Just like you speak English to talk to friends, you write Python to talk to computers.

Why is it called Python? 🐍 Not because of the snake! The creator loved a comedy show called “Monty Python’s Flying Circus”!

Your First Python Command

print("Hello, World!")

What happens? The computer shows: Hello, World!

It’s like telling your robot friend: “Say hello to everyone!”

📦 Variables and Data Types: Labeled Boxes

What are Variables?

Imagine you have labeled boxes in your room:

• 📦 Box labeled “age” → holds the number 10
• 📦 Box labeled “name” → holds “Alex”
• 📦 Box labeled “is_happy” → holds True or False

Variables are just named containers that store information!

age = 10
name = "Alex"
is_happy = True

Data Types: What Goes in the Boxes?

my_age = 25          # int (integer)
my_height = 5.8      # float (decimal)
my_name = "Sam"      # str (string)
is_student = True    # bool (boolean)

Quick Tip:

• Use quotes " " or ' ' for text
• No quotes for numbers

➕ Python Operators: The Action Heroes

Operators are like magic wands that make things happen!

Arithmetic Operators (Math Magic)

cookies = 10
friends = 3
each_gets = cookies // friends  # 3
leftover = cookies % friends     # 1

Comparison Operators (True or False?)

Logical Operators (Combining Conditions)

📝 Strings in Python: Playing with Text

Strings are like beads on a necklace – each letter is one bead!

Creating Strings

greeting = "Hello"
name = 'Python'
message = """This is a
multi-line string!"""

String Superpowers

word = "Python"

# Length (how many letters?)
len(word)          # 6

# Grab one letter (counting from 0!)
word[0]            # 'P'
word[-1]           # 'n' (last letter)

# Slice (grab a piece)
word[0:3]          # 'Pyt'

String Methods (Special Tricks)

text = "hello world"

text.upper()       # "HELLO WORLD"
text.lower()       # "hello world"
text.title()       # "Hello World"
text.replace("hello", "hi")  # "hi world"
text.split(" ")    # ["hello", "world"]

Joining Strings Together

first = "Hello"
second = "World"

# Using +
result = first + " " + second  # "Hello World"

# Using f-strings (the cool way!)
name = "Alex"
age = 10
intro = f"I'm {name}, age {age}"
# "I'm Alex, age 10"

📋 Lists and Tuples: Collections of Things

Lists: The Shopping Basket 🛒

A list is like a shopping basket – you can add, remove, and change items!

fruits = ["apple", "banana", "cherry"]
numbers = [1, 2, 3, 4, 5]
mixed = [1, "hello", True, 3.14]

List Actions:

fruits = ["apple", "banana"]

# Add to end
fruits.append("cherry")
# ["apple", "banana", "cherry"]

# Remove item
fruits.remove("banana")
# ["apple", "cherry"]

# Access by position (starts at 0!)
fruits[0]    # "apple"
fruits[-1]   # "cherry" (last one)

# Change an item
fruits[0] = "mango"
# ["mango", "cherry"]

# How many items?
len(fruits)  # 2

Tuples: The Sealed Box 📦🔒

A tuple is like a sealed box – once packed, you can’t change what’s inside!

coordinates = (10, 20)
colors = ("red", "green", "blue")

# Access works the same
colors[0]    # "red"
colors[-1]   # "blue"

# But you CAN'T change them!
# colors[0] = "yellow"  ← ERROR!

Why use tuples? When you want data to stay safe and unchanged!

graph TD
    A["Collections"] --> B["List"]
    A --> C["Tuple"]
    B --> D["✅ Can change<br/>✅ Can add/remove<br/>📝 Use [ ]"]
    C --> E["🔒 Cannot change<br/>❌ Fixed size<br/>📝 Use #40; #41;"]

📚 Dictionaries and Sets: Smart Storage

Dictionaries: The Contact Book 📇

A dictionary stores pairs: a name (key) and its information (value).

student = {
    "name": "Alex",
    "age": 10,
    "grade": "5th"
}

# Get a value using its key
student["name"]      # "Alex"
student["age"]       # 10

# Add new pair
student["school"] = "Sunny Elementary"

# Change a value
student["age"] = 11

# Remove a pair
del student["grade"]

Dictionary Methods:

person = {"name": "Sam", "age": 25}

person.keys()    # ["name", "age"]
person.values()  # ["Sam", 25]
person.items()   # [("name","Sam"), ("age",25)]
person.get("name")  # "Sam"

Sets: The Unique Collection 🎯

A set only keeps unique items – no duplicates allowed!

colors = {"red", "blue", "green"}
numbers = {1, 2, 2, 3, 3, 3}  # becomes {1, 2, 3}

# Add item
colors.add("yellow")

# Remove item
colors.remove("red")

# Check if exists
"blue" in colors  # True

Set Magic: Finding Common Things

set_a = {1, 2, 3, 4}
set_b = {3, 4, 5, 6}

set_a & set_b   # {3, 4} - in both
set_a | set_b   # {1,2,3,4,5,6} - all unique
set_a - set_b   # {1, 2} - only in A

🚦 Conditional Statements: Making Decisions

Conditionals are like traffic lights – they tell Python which way to go!

The IF Statement

age = 10

if age >= 18:
    print("You can vote!")
else:
    print("You're too young to vote")

Adding More Options: elif

score = 85

if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
else:
    grade = "F"

print(f"Your grade: {grade}")  # "Your grade: B"

Flow Diagram:

graph TD
    A["Start"] --> B{score >= 90?}
    B -->|Yes| C["grade = A"]
    B -->|No| D{score >= 80?}
    D -->|Yes| E["grade = B"]
    D -->|No| F{score >= 70?}
    F -->|Yes| G["grade = C"]
    F -->|No| H["grade = F"]

Combining Conditions

age = 15
has_ticket = True

if age >= 12 and has_ticket:
    print("Enjoy the movie!")
elif age < 12 and has_ticket:
    print("Need parent with you")
else:
    print("Please buy a ticket")

🔄 Loops in Python: Repeat, Repeat, Repeat!

Loops are like a music player on repeat – they do the same thing over and over!

FOR Loop: When You Know How Many Times

# Print numbers 1 to 5
for i in range(1, 6):
    print(i)
# Output: 1, 2, 3, 4, 5

# Loop through a list
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(f"I love {fruit}!")

WHILE Loop: Until Something Changes

count = 0
while count < 5:
    print(count)
    count = count + 1
# Output: 0, 1, 2, 3, 4

⚠️ Warning: Always make sure the loop can end, or it runs forever!

Loop Controls

# Find first even number
for num in [1, 3, 4, 7, 8]:
    if num % 2 == 0:
        print(f"Found: {num}")
        break
# Output: Found: 4

# Skip odd numbers
for num in range(1, 6):
    if num % 2 != 0:
        continue
    print(num)
# Output: 2, 4

Nested Loops (Loop Inside Loop)

# Multiplication table (1-3)
for i in range(1, 4):
    for j in range(1, 4):
        print(f"{i} x {j} = {i*j}")

Output:

1 x 1 = 1
1 x 2 = 2
1 x 3 = 3
2 x 1 = 2
...

🎯 Quick Summary: Your Python Toolkit

🌈 You Did It!

You’ve just learned the building blocks of Python! Remember:

• Variables store things
• Strings handle text
• Lists and Tuples collect items
• Dictionaries pair keys with values
• If/Else makes decisions
• Loops repeat actions

Now go practice and build something amazing! 🚀

“The best way to learn Python is by writing Python!”