Python Basics — Assignment & Bitwise Operators

Assignment & Bitwise Operators

Assignment operators store (and optionally modify) values in variables. Bitwise operators work on the individual bits of integer values.

Assignment Operators

Operator	Example	Equivalent To
=	x = 5	Assign 5 to x
+=	x += 3	x = x + 3
-=	x -= 3	x = x - 3
*=	x *= 3	x = x * 3
/=	x /= 3	x = x / 3
//=	x //= 3	x = x // 3
%=	x %= 3	x = x % 3
**=	x **= 3	x = x ** 3

Examples

x = 10
print(x)    # 10

x += 5      # x = x + 5
print(x)    # 15

x -= 3      # x = x - 3
print(x)    # 12

x *= 2      # x = x * 2
print(x)    # 24

x //= 5     # x = x // 5
print(x)    # 4

x **= 3     # x = x ** 3
print(x)    # 64

x %= 10     # x = x % 10
print(x)    # 4

Augmented assignment also works with strings and lists:

text = "Hello"
text += " World"
print(text)  # Hello World

items = [1, 2]
items += [3, 4]
print(items)  # [1, 2, 3, 4]

Walrus Operator (:=)

The walrus operator (:=), introduced in Python 3.8, assigns a value to a variable as part of an expression. It’s called the walrus operator because := looks like a walrus on its side.

# Without walrus operator
data = input("Enter a number: ")
if len(data) > 0:
    print(f"You entered: {data}")

# With walrus operator — assign and test in one step
if (data := input("Enter a number: ")):
    print(f"You entered: {data}")

Practical Use Cases

# Reading lines from a file
# while (line := file.readline()):
#     process(line)

# Avoiding repeated computation
import random
numbers = [random.randint(1, 20) for _ in range(10)]

# Filter and capture at the same time
big = [n for n in numbers if (square := n ** 2) > 100]

Note: The walrus operator is optional. If it feels confusing, stick with regular assignment. Readability matters more.

Bitwise Operators

Bitwise operators work on the binary representation of integers:

Operator	Name	Example	Result	Binary Explanation
&	AND	5 & 3	1	101 & 011 = 001
\|	OR	5 \| 3	7	101 \| 011 = 111
^	XOR	5 ^ 3	6	101 ^ 011 = 110
~	NOT	~5	-6	Inverts all bits
<<	Left shift	5 << 1	10	101 → 1010
>>	Right shift	5 >> 1	2	101 → 10

Understanding Binary

# View binary representation
print(bin(5))    # 0b101
print(bin(3))    # 0b11
print(bin(10))   # 0b1010

# Convert binary string to integer
print(int("101", 2))   # 5
print(int("1010", 2))  # 10

Bitwise AND (&)

Returns 1 only where both bits are 1:

a = 5   # 101
b = 3   # 011
print(a & b)  # 1 (001)

#   101
# & 011
# -----
#   001 = 1

Bitwise OR (|)

Returns 1 where at least one bit is 1:

a = 5   # 101
b = 3   # 011
print(a | b)  # 7 (111)

Bitwise XOR (^)

Returns 1 where bits are different:

a = 5   # 101
b = 3   # 011
print(a ^ b)  # 6 (110)

Bit Shifting

# Left shift — multiply by 2^n
print(5 << 1)   # 10 (5 × 2)
print(5 << 2)   # 20 (5 × 4)
print(1 << 10)  # 1024 (2^10)

# Right shift — divide by 2^n (floor)
print(20 >> 1)  # 10 (20 ÷ 2)
print(20 >> 2)  # 5 (20 ÷ 4)

When to Use Bitwise Operations

For beginners, bitwise operators are rarely needed. They show up in:

Use Case	Example
Permissions/Flags	File permissions: rwx = 0b111
Performance	x << 1 instead of x * 2
Networking	IP address masks, subnet calculation
Cryptography	XOR encryption
Low-level programming	Hardware registers, embedded systems

Augmented Bitwise Assignment

x = 5
x &= 3    # x = x & 3 → 1
x |= 6    # x = x | 6 → 7
x ^= 2    # x = x ^ 2 → 5
x <<= 1   # x = x << 1 → 10
x >>= 2   # x = x >> 2 → 2

Common Mistakes

Mistake	Example	Fix
& instead of and	if x & y: (bitwise)	Use and for logic
\| instead of or	if x \| y: (bitwise)	Use or for logic
Walrus in wrong context	x := 5 (bare statement)	Use in expressions: if (x := 5):

Summary

• Augmented assignment (+=, -=, etc.) modifies and reassigns in one step
• The walrus operator (:=) assigns within an expression (Python 3.8+)
• Bitwise operators (&, |, ^, ~, <<, >>) work on binary bits
• Use and/or for logical operations, &/| for bitwise operations
• Bitwise operations are advanced — focus on assignment operators first

---

Next up: Identity & Membership Operators →