🚀 PYTHON ESSENTIALS FOR AI/ML (Variables Loops Functions)

1️⃣ Variables

✔ Quick explanation

A variable is a name that stores a value in memory so you can reuse it.

✔ Real-life analogy

Think of a tiffin box with a label:

• Label = variable name
• Food inside = value

You can change the food anytime; the label stays.

✔ Syntax

x = 10
name = "Ali"
price = 99.5
is_active = True

✔ Real-life ML example

When training a model:

learning_rate = 0.001
epochs = 20
batch_size = 32

✔ Important note

Python decides the data type automatically.

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2️⃣ Loops

Loops help you repeat tasks without writing repeated code.

🔹 for loop

Used when you know how many times to repeat.

Example

fruits = ["apple", "banana", "mango"]
for f in fruits:
    print(f)

Output:

apple
banana
mango

Real-life analogy

You check every message in WhatsApp one by one → a loop.

ML example

Looping through data batches:

for batch in data_loader:
    train(batch)

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🔹 while loop

Used when you don’t know how many times but want to repeat until a condition becomes false.

Example

count = 1
while count <= 5:
    print(count)
    count += 1

Real-life analogy

You keep scrolling Instagram until your battery is dead.
"Bhai jab tak battery > 0, loop chalta rahega."

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3️⃣ Functions

Functions are reusable blocks of code.

✔ Why functions?

• Avoid repeating code
• Keep logic clean & modular
• Essential for ML pipeline (data cleaning, model training, evaluation)

✔ Syntax

def greet(name):
    return "Hello " + name

Using it:

print(greet("Ali"))

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Real-life example

You cook maggi in a fixed process:

1. Boil water
2. Add masala
3. Add noodles
4. Serve

This whole process is a function.

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ML example

def train_model(model, data, epochs):
    for epoch in range(epochs):
        model.train(data)

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🔥 Putting it all together

def square_numbers(nums):
    result = []                 # variable (list)
    for n in nums:              # for loop
        result.append(n*n)
    return result               # function output

numbers = [2, 3, 5]
print(square_numbers(numbers))

Output:

[4, 9, 25]

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⚠ Common Mistakes

• Missing indentation (Python is strict).
• Forgetting : after loops & function definitions.
• Wrong variable names like 1var (names cannot start with a number).
• Infinite while loops (while True: without break).

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🧠 Mini Quiz

Try to answer mentally.

Q1

What will this print?

x = 5
while x < 8:
    print(x)
    x = x + 1

Q2

Write a function that returns the cube of a number.

Q3

What type of loop would you use to train a model until loss < 0.01?