Python Arithmetic Operators

In the last lesson you learned about the Python Data Types Overview. Numbers were one of the main types there. Now we get to actually do something with those numbers. We want to add them. We want to multiply them. We want to split a bill or check if a number is even. For all of that you need arithmetic operators. These are the little symbols that tell Python to do math.

🤔 Why Do We Need Arithmetic Operators?

Say you are building a shopping cart. Someone buys 3 items at 250 each. You need the total. Or you split a dinner bill of 1000 between 4 friends. You want each share. You can not just stare at the numbers and hope for an answer. You need to tell the computer to calculate.

Arithmetic operators are how you say “do this math” in Python. They look just like the symbols you used in school. There are also a couple of new ones for things school did not cover.

➕ The Basic Four: Add, Subtract, Multiply, Divide

These four are the ones you already know from a calculator. The symbols are simple.

Here is each one doing its job:

print(10 + 3)   # add
print(10 - 3)   # subtract
print(10 * 3)   # multiply
print(10 / 3)   # divide

13
7
30
3.3333333333333335

Add, subtract, and multiply behave exactly how you would expect. The one to watch is divide, the / symbol.

See how 10 / 3 gave 3.3333333333333335 and not just 3? That is on purpose. In Python the / operator always gives a float. A float is a number with a decimal point. So even 10 / 2 gives 5.0, not 5. Keep that in mind. Sometimes you want a clean whole number instead. We will fix that in a second.

🔢 Floor Division: When You Want a Whole Number

Here is the pain. You have 7 cookies and 2 children. 7 / 2 gives 3.5. But you can not give half a cookie to a child. You want to know how many whole cookies each child gets. That is what floor division is for. Its symbol is //, which is two slashes.

This is the same division. But it throws away the decimal part and keeps the whole number:

print(7 // 2)    # how many whole cookies each child gets
print(10 // 3)
print(20 // 6)

3
3
3

So 7 // 2 is 3, not 3.5. The // does not round to the nearest number. It always goes down to the whole number below. That is why it is called floor division. The word “floor” means round down.

➗ Modulo: The Remainder Left Over

Okay. Floor division told us each child gets 3 whole cookies. But 2 children times 3 cookies is 6 cookies. We had 7. So 1 cookie is left over. How do we get that leftover number?

That leftover is called the remainder. The operator that gives it is %, called modulo. People often read it as “mod”.

print(7 % 2)     # 1 cookie left over
print(10 % 3)    # what is left after taking out whole 3s
print(20 % 5)    # divides evenly, nothing left

1
1
0

Read it like this. 7 % 2 asks “after splitting 7 into groups of 2, how much is left?” The answer is 1. And 20 % 5 gives 0 because 5 divides 20 perfectly. Nothing is left over.

Making Modulo Click: Is a Number Even?

Here is the most common real use of %. You often need to know if a number is even or odd. Think of coloring every second row of a table. Or splitting people into two teams.

An even number divides by 2 with nothing left over. An odd number always leaves 1. So you just check the remainder when you divide by 2:

n = 8
print(n % 2)     # 0 means even

n = 7
print(n % 2)     # 1 means odd

0
1

So the rule is simple. If n % 2 is 0, the number is even. If it is 1, the number is odd. You will use this trick again and again once you start writing real programs.

⬆️ Exponent: Raising to a Power

The last operator is for powers. Say you want 2 to the power of 10. Or you want to square a number. The symbol is **, which is two stars. It is called the exponent operator.

print(2 ** 3)    # 2 multiplied by itself 3 times
print(5 ** 2)    # 5 squared
print(9 ** 0.5)  # power of 0.5 is the square root

8
25
3.0

So 2 ** 3 means 2 times 2 times 2, which is 8. And 5 ** 2 is 5 squared, which is 25. Here is a nice bonus. Raising a number to the power of 0.5 gives its square root. So 9 ** 0.5 gives 3.0.

📋 All the Operators at a Glance

Here are all seven in one place. You can come back and look them up any time.

🧮 Operator Precedence: Who Goes First?

Now, what happens when you mix operators in one line? Python does not just go left to right. It follows an order. It is the same order you learned in math class.

The short version, from first to last:

• ** (exponent) happens first
• then *, /, //, % (multiply and divide kinds)
• then + and - (add and subtract) last

So in 2 + 3 * 4, the multiply runs first. That gives 2 + 12, which is 14. It is not 5 * 4.

print(2 + 3 * 4)      # multiply first, then add
print(2 ** 3 * 2)     # power first, then multiply

14
16

If you want a different order, use parentheses. These are the round symbols ( ). Whatever is inside ( ) runs first, always. Parentheses let you force the order you actually want:

print((2 + 3) * 4)    # parentheses force the add to run first

20

See the difference? Without parentheses you got 14. With parentheses around 2 + 3, the add runs first and you get 20.

🛒 A Combined Example

Let us put it together with that shopping cart from the start. Someone buys 3 items at 250 each. There is a flat 50 delivery fee. And they have a coupon that takes 10% off the items only.

price = 250
quantity = 3
delivery = 50

items_total = price * quantity        # 750
discount = items_total * 10 / 100     # 75
final = items_total - discount + delivery

print("Items total:", items_total)
print("Discount:", discount)
print("You pay:", final)

Items total: 750
Discount: 75.0
You pay: 725.0

Walk through it. price * quantity gives the items total of 750. Then items_total * 10 / 100 works out the 10% discount, which is 75. Multiply and divide have the same rank. So Python reads them left to right. First 750 * 10 is 7500. Then divide by 100 gives 75. Finally we subtract the discount and add delivery. That gives what the user pays.

⚠️ Common Mistakes

A few traps catch almost everyone at the start. Watch for these.

• Expecting / to give a whole number. It never does. 10 / 2 is 5.0, a float. Use // when you want a plain whole number.

• Mixing up // and %. Floor division // gives the whole groups. Modulo % gives the leftover. They answer different questions.

• Using ^ for power. In many places ^ means “to the power”, but not in Python. Always use ** for powers.

# ❌ Avoid: ^ does not mean power in Python
print(2 ^ 3)     # gives 1, not 8 — here ^ is the bitwise XOR operator, not power

# ✅ Good: ** is the power operator
print(2 ** 3)    # gives 8

• Forgetting precedence. 100 - 10 * 2 is 80, not 180. The multiply runs before the subtract. Add parentheses if you meant the other order.

✅ Best Practices

Small habits that keep your math correct and easy to read.

• Use // when you genuinely want a whole number, like splitting people into equal teams. Use / when a decimal answer is fine.

• Reach for % 2 whenever you need an even or odd check. It is the standard way. Other coders will read it instantly.

• Add parentheses around any math that is even slightly tricky. Clear beats clever.

• Put spaces around your operators. Write a + b, not a+b. It reads much easier and is the normal Python style.

🧩 What You’ve Learned

A quick recap of what you can now do.

• ✅ Do basic math with +, -, *, and /, and remember that / always gives a float.
• ✅ Use // for floor division when you want a whole number, rounded down.
• ✅ Use % to get the remainder, and check even or odd with n % 2.
• ✅ Raise numbers to a power with **, including square roots using ** 0.5.
• ✅ Follow operator precedence (** first, then * / // %, then + -) and force any order you want with parentheses.

🚀 What’s Next?

You can do math now. But real programs also need to compare values. Think of checking if a price is greater than your budget. That is exactly what comparison operators do next.

Comparison Operators