Table of Contents

• Variable Naming Conventions
• F-String
• Order of Functions in Python
• Dictionaries in Python
• Sets in Python
• Multiple Return Values in Python

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Variable Naming Conventions

Variable names cannot contain spaces. Use readable formats like:

“Please use snake_case for variable names.” — Guido van Rossum, Creator of Python

Common Naming Styles

Name	Description	Example	Common In
Snake Case	Lowercase words separated by underscores	my_hero_health	Python, Ruby, Rust
Camel Case	Each word capitalized except the first	myHeroHealth	JavaScript, Java
Pascal Case	All words capitalized	MyHeroHealth	C#, C++

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F-String

• Use f before the string.
• Variables inside {} are injected.

name = "Adarsh"
greeting = f"Hello, {name}!"
print(greeting)  # Output: Hello, Adarsh!

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Order of Functions in Python

Functions must be defined before used. Python reads top to bottom.

Best Practice Define all helper functions first. Call main() last.

def main():
    health = 10
    armor = 5
    add_armor(health, armor)

def add_armor(h, a):
    new_health = h + a
    print_health(new_health)

def print_health(new_health):
    print(f"The player now has {new_health} health")

main()

Use main() for structure, even though not required.

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Dictionaries in Python

Dictionaries store data in key → value pairs.

car = {
  "brand": "Toyota",
  "model": "Camry",
  "year": 2019
}

• Keys must be unique.
• Duplicate keys? Last one wins:

car = {"brand": "Toyota", "brand": "Honda"}
print(car["brand"])  # Output: Honda

Deleting Keys

del car["year"]

• del on a non-existent key raises KeyError.
• Python 3.7+ maintains insertion order in dictionaries.

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Sets in Python

Sets are unordered collections with unique elements.

fruits = {"apple", "banana", "grape"}
print(type(fruits))

Adding to a Set

fruits.add("pear")

• Adding duplicates does nothing.

Empty Set

empty_set = set()  # NOT {}

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Multiple Return Values in Python

Functions can return multiple values using commas:

def cast_spell(level, mana):
    return level * 2, mana - 10

Unpacking Return Values

dmg, mana_left = cast_spell(5, 100)
print(f"Damage: {dmg}, Remaining Mana: {mana_left}")

• Python returns values as a tuple under the hood.