Python Assignment Operators with Examples

Assignment operators store a value in a variable. The basic one is =. The others, called augmented assignment operators, update a variable using its current value: score += 5 is a short way of writing score = score + 5. You will use them constantly in loops, counters and running totals.

Python Assignment Operators Table

Operator	Example	Same as
=	x = 10	store 10 in x
+=	x += 5	x = x + 5
-=	x -= 3	x = x - 3
*=	x *= 2	x = x * 2
/=	x /= 4	x = x / 4
//=	x //= 5	x = x // 5
%=	x %= 5	x = x % 5
**=	x **= 4	x = x ** 4
&=, |=, ^=	x &= 10	x = x & 10 (bitwise)
<<=, >>=	x <<= 2	x = x << 2
:=	(n := len(data))	assign inside an expression (“walrus”)

Arithmetic Assignment Operators

x = 10
x += 5
print(x)
x -= 3
print(x)
x *= 2
print(x)
x /= 4
print(x)

x = 17
x //= 5
print(x)
x = 17
x %= 5
print(x)
x = 3
x **= 4
print(x)

Output:

15
12
24
6.0
3
2
81

Notice that x /= 4 turns x into a float (6.0), because / always gives a float. Use //= if you want to stay with whole numbers.

Bitwise Assignment Operators

f = 12
f &= 10
print(f)
f |= 1
print(f)
f ^= 3
print(f)
f <<= 2
print(f)
f >>= 1
print(f)

Output:

8
9
10
40
20

These follow the same rules as the bitwise operators; they just store the result back in the variable.

Assigning Many Variables at Once

a, b, c = 1, 2, 3
print(a, b, c)

p = q = r = 0
print(p, q, r)

a, b = b, a        # swap without a temporary variable
print(a, b)

first, *rest = [10, 20, 30, 40]
print(first, rest)

Output:

1 2 3
0 0 0
2 1
10 [20, 30, 40]

The starred name *rest collects all the remaining items into a list. This is called unpacking.

Assignment Operators with Strings and Lists

greeting = "Hello"
greeting += ", Riya"
print(greeting)

line = "-" * 3
line *= 2
print(line)

nums = [1, 2]
nums += [3]
print(nums)

Output:

Hello, Riya
------
[1, 2, 3]

The Walrus Operator :=

Added in Python 3.8, := lets you assign a value inside an expression, so you don’t have to compute it twice:

data = [4, 8, 15, 16, 23, 42]
if (n := len(data)) > 5:
    print(f"List is long: {n} items")

Output:

List is long: 6 items

A Trap: += on Lists Changes the Shared List

For a mutable object like a list, += changes the list in place. If two names point to the same list, both see the change. Tuples are immutable, so += creates a new tuple instead:

list_a = [1, 2]
list_b = list_a
list_b += [3]
print(list_a)

t = (1, 2)
t2 = t
t2 += (3,)
print(t, t2)

Output:

[1, 2, 3]
(1, 2) (1, 2, 3)

If you want a separate list, make a copy first: list_b = list_a.copy().

Common Mistakes

• Writing x =+ 5 instead of x += 5. x =+ 5 is valid Python, but it means x = +5, so x simply becomes 5.
• Using x++. Python has no ++ or -- operator. Use x += 1.
• Using a variable before giving it a value. total += marks fails with a NameError if total was never set. Start with total = 0.

Practice Questions

1. What does this print? k = 7; k += k; print(k)
2. What does this print? k = 20; k //= 3; k **= 2; print(k)

Answers: 1) 14. 2) 36, because 20 // 3 is 6 and 6 ** 2 is 36.

Frequently Asked Questions

What is the difference between = and == in Python?

= stores a value in a variable. == compares two values and returns True or False.

Is x += 1 the same as x = x + 1?

For numbers and strings, yes. For lists, += changes the existing list in place, while x = x + [1] creates a new list.

What is the walrus operator in Python?

:=, which assigns a value inside an expression, such as an if or while condition. It needs Python 3.8 or newer.

Next: Python logical operators · Previous: Python arithmetic operators · All operators: Python operators overview