bin()

bin(x)

Returns: str · Updated March 13, 2026 · Built-in Functions

built-in conversion binary numbers

The bin() function converts an integer to a binary string representation prefixed with 0b. It is the quickest way to get the binary representation of any integer in Python.

Syntax

bin(x)

Parameters

Parameter	Type	Default	Description
`x`	`int`	—	An integer to convert to binary. Floats will raise a TypeError.

Examples

Basic usage

# Convert an integer to binary
result = bin(10)
print(result)
# 0b1010

Using with other numbers

# Zero
print(bin(0))
# 0b0

# Negative numbers include the negative sign
print(bin(-10))
# -0b1010

# Large numbers work fine
print(bin(255))
# 0b11111111

Converting back to int

# The int() function can parse binary strings
binary_str = bin(42)
print(binary_str)
# 0b101010

# Parse it back using base 2
back_to_int = int(binary_str, 2)
print(back_to_int)
# 42

# Or use the prefix-agnostic approach
print(int('101010', 2))
# 42

Practical: Bit operations

# Check if a number is even using bitwise AND
num = 7
if num & 1:
    print(f"{num} is odd")
else:
    print(f"{num} is even")
# 7 is odd

# bin helps visualize what's happening
print(bin(7 & 1))
# 0b1 (truthy)

# Check specific bit positions
position = 2
bit_value = 4  # 2^2
number = 10

print(f"Is bit {position} set in {number}? {bool(number & bit_value)}")
# Is bit 2 set in 10? True

print(f"Binary of 10: {bin(10)}")
# Binary of 10: 0b1010

Working with byte data

# Convert a byte to its binary representation
byte_value = 0b11001010
print(bin(byte_value))
# 0b11001010

# Extract individual bits
for i in range(7, -1, -1):
    bit = (byte_value >> i) & 1
    print(bit, end='')
# 11001010

Common Patterns

Formatting without the prefix

# Remove the '0b' prefix
num = 42
binary_without_prefix = bin(num)[2:]  # Slice off '0b'
print(binary_without_prefix)
# 101010

# Pad to fixed width
print(bin(5)[2:].zfill(8))
# 00000101

Validation and checking

# Check if a number is a power of 2
def is_power_of_two(n):
    return n > 0 and (n & (n - 1)) == 0

print(is_power_of_two(8))   # True
print(is_power_of_two(10))  # False
print(is_power_of_two(0))   # False

# Count set bits (population count)
def count_bits(n):
    return bin(n).count('1')

print(count_bits(255))  # 8
print(count_bits(7))    # 3

Errors

TypeError with non-integers

# This will raise TypeError
bin(3.14)
# TypeError: 'float' object cannot be interpreted as an integer

# Strings need conversion first
int("1010", 2)  # 10, then bin(10) works

Converting strings directly

# This raises ValueError
bin("1010")
# TypeError: object cannot be interpreted as an integer

# Convert string to int first
bin(int("1010", 2))
# 0b1010