What is the difference between / and //?

/ performs true division and returns a float for ordinary numeric operands. // performs floor division, rounding the quotient down toward negative infinity.

What is short-circuit evaluation?

With and, Python stops when the left operand is falsey; with or, it stops when the left operand is truthy. The right operand is evaluated only if needed.

What is the difference between == and is?

== tests equality of value; is tests object identity. Use == for values and is None for a None check.

PythonVariables and Basic Databeginner25 min read

Operators in Python

Use arithmetic, comparison, logical, assignment, membership, and identity operators correctly.

In this lesson, you will learn:

Use arithmetic and augmented-assignment operators.
Compare values with comparison operators.
Combine conditions with and, or, and not.
Apply precedence and parentheses to expressions.
Use membership and identity operators appropriately.
Explain floor division, modulo, and short-circuit evaluation.

1. Arithmetic operators

The main arithmetic operators are + (addition), - (subtraction), * (multiplication), / (true division), // (floor division), % (modulo), and ** (exponentiation). For ordinary numeric operands, / produces a float result even when the division is exact.

Floor division rounds the mathematical quotient down toward negative infinity. Modulo returns the remainder associated with floor division; with a nonzero divisor, the result has the divisor’s sign.

Floor division and modulo with negatives

python

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print(7 // 3)
print(7 % 3)
print(-7 // 3)
print(-7 % 3)

Output

2 1 -3 2

7 divided by 3 has floor quotient 2 and remainder 1. The mathematical quotient -7 / 3 is about -2.333, whose floor is -3. Because the divisor is positive 3, the modulo result is 2, satisfying -7 == (-3 * 3) + 2.

Key Point

Use parentheses to make complex arithmetic easier to read, even when you know the precedence rules.

Operator	Meaning	Example result
+	Addition	7 + 2 → 9
-	Subtraction	7 - 2 → 5
*	Multiplication	7 * 2 → 14
/	True division	7 / 2 → 3.5
//	Floor division	7 // 2 → 3
%	Modulo/remainder	7 % 2 → 1
**	Exponentiation	2 ** 3 → 8

2. Comparison operators

Comparison operators compare values and produce a Boolean result: ==, !=, <, <=, >, and >=. Use == to compare values for equality and != to check that they differ.

Python also supports chained comparisons, such as 0 <= score <= 100, which means score is at least 0 and at most 100.

Compare values

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score = 85
print(score >= 50)
print(score == 100)
print(0 <= score <= 100)

Output

True False True

85 is at least 50. 85 is not equal to 100. The chained comparison checks both bounds.

3. Logical operators

and is true when both operands are truthy; or is true when at least one operand is truthy; not reverses the truth value. Python evaluates and and or from left to right and uses short-circuit evaluation.

Unlike some languages, and and or return one of their operands, not necessarily a Boolean object. In an if condition this usually works as expected because Python tests truthiness.

Combine conditions

python

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age = 22
has_id = True
print(age >= 18 and has_id)
print(age < 18 or has_id)
print(not has_id)

Output

True True False

Both parts of the first condition are true. The second condition is true because has_id is true. not True evaluates to False.

Short-circuit evaluation

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def check():
    print("checked")
    return True

print(False and check())
print(True or check())

Output

False True

False and ... stops immediately because the result cannot become true; check() is not called. True or ... stops immediately because the result is already true; check() is not called. Therefore checked is never printed.

4. Assignment and augmented assignment

The = operator assigns or rebinds a name. Augmented assignment operators such as +=, -=, *=, and /= combine an operation with assignment. For immutable numeric values, x += 2 is similar in effect to x = x + 2.

For mutable objects, augmented assignment can behave differently from a plain reassignment. For example, list += iterable commonly extends the existing list in place. The exact behavior depends on the object type.

Update a running total

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total = 10
total += 5
total *= 2
print(total)

Output

total += 5 updates total from 10 to 15. total *= 2 updates it from 15 to 30.

5. Operator precedence and parentheses

Precedence determines which operations group first. For example, multiplication has higher precedence than addition, so 2 + 3 * 4 is evaluated as 2 + (3 * 4). Parentheses can explicitly control grouping and make intent clearer.

Exponentiation ** groups from right to left, so 2 ** 3 ** 2 means 2 ** (3 ** 2), which is 512. Use parentheses when a reader might otherwise have to remember a rule.

Make grouping explicit

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print(2 + 3 * 4)
print((2 + 3) * 4)
print(2 ** 3 ** 2)

Output

14 20 512

Multiplication happens before addition, giving 14. Parentheses make addition happen first, giving 20. Exponentiation groups from the right, so 2 ** (3 ** 2) equals 512.

6. Membership operators

in tests whether a value is present in a container or sequence; not in tests whether it is absent. For strings, membership checks for a substring. For dictionaries, membership checks keys, not values.

Check membership

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colors = ["red", "blue"]
profile = {"name": "Asha", "active": True}
print("red" in colors)
print("green" not in colors)
print("name" in profile)
print("Asha" in profile)

Output

True True True False

red is an element of the list. green is absent from the list. name is a dictionary key. Asha is a dictionary value, not a key.

7. Identity operators

is checks whether two references point to the same object; is not checks that they do not. It is not a replacement for ==. Two separate lists can contain equal values but still be different objects.

A common and appropriate identity check is value is None. Avoid relying on object identity for numbers or strings just because a particular Python run appears to reuse an object.

Equality is not identity

python

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a = [1, 2]
b = [1, 2]
print(a == b)
print(a is b)
result = None
print(result is None)

Output

True False True

The two lists compare equal by contents. They are separate list objects, so identity is false. is None is the recommended way to test for None.

Common Pitfalls & Mistakes to Avoid

#1 Using / when integer floor division is required.

Explanation: Use // for floor division; note that it rounds down, so -7 // 3 is -3.

#2 Assuming modulo is always positive.

Explanation: For a nonzero divisor, the modulo result has the divisor’s sign; -7 % 3 is 2.

#3 Using is to compare ordinary values.

Explanation: Use == for equality and is for identity, especially checks against None.

#4 Assuming and and or always return True or False.

Explanation: They return an operand and use truthiness to decide whether to evaluate the next operand.

#5 Forgetting operator precedence.

Explanation: Use parentheses when needed to make the intended grouping explicit.

Practice Questions

Set price = 18 and quantity = 4. Calculate total using multiplication, then apply a discount of 5 using augmented assignment. Print the final total.

Given score = 78, print True only if the score is between 0 and 100 inclusive and is at least 40.