In Python, you can handle numbers and strings as binary (bin), octal (oct), and hexadecimal (hex) as well as decimal. They can also be converted to each other.

This article describes the following contents.

Write integers in binary, octal, and hexadecimal notation

Convert a numbers to a binary, octal, and hexadecimal string

bin(), oct(), hex()

format(), str.format(), f-strings

Convert a negative integer to a string in two's complement representation

Convert a binary, octal, and hexadecimal string to a number

int()

Usage examples

Binary string arithmetic

Convert between binary, octal, and hexadecimal numbers

See the following article for the basics of conversion between the string (str) and the number (int, float).

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Convert a string to a number (int, float) in Python⁠

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Write integers in binary, octal, and hexadecimal notation

By adding the prefixes 0b, 0o, and 0x, integer type int numbers can be written in binary, octal, and hexadecimal, respectively. The output of print() will be in decimal notation.

bin_num = 0b10

oct_num = 0o10

hex_num = 0x10

print(bin_num)

print(oct_num)

print(hex_num)

# 2

# 8

# 16

source:

numeric_types.py⁠

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You can also use uppercase 0B, 0O, and 0X.

Bin_num = 0B10

Oct_num = 0O10

Hex_num = 0X10

print(Bin_num)

print(Oct_num)

print(Hex_num)

# 2

# 8

# 16

source:

numeric_types.py⁠

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Even with a prefix, the type is an integer int.

print(type(bin_num))

print(type(oct_num))

print(type(hex_num))

# <class 'int'>

print(type(Bin_num))

print(type(Oct_num))

print(type(Hex_num))

# <class 'int'>

source:

numeric_types.py⁠

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Since they are int, they can be operated as usual.

result = 0b10 * 0o10 + 0x10

print(result)

# 32

source:

numeric_types.py⁠

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In Python3.6 and later, you can insert underscores _ in numbers.Repeating the underscore _ raises an error, but you can insert as many as you like if it is not repeated.

The underscore _ can be used as a delimiter when there are many digits. For example, it is easier to read if you enter _ every four digits.

print(0b111111111111 == 0b1_1_1_1_1_1_1_1_1_1_1_1)

# True

bin_num = 0b1111_1111_1111

print(bin_num)

# 4095

source:

numeric_types.py⁠

⁠

Convert a number to a binary, octal, and hexadecimal string

You can use the following functions to convert a number to a binary, octal, or hexadecimal string.

Built-in function bin(), oct(), hex()

Built-in function format(), string method str.format(), f-strings

It also describes how to get a string in two's complement representation for a negative value.

bin(), oct(), hex()

The built-in functions bin(), oct(), and hex() can be used to convert a number to a binary, octal, and hexadecimal string. These functions return a string with the prefixes 0b,0o, and 0x, respectively.

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Built-in Functions - bin() — Python 3.9.1 documentation⁠

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Built-in Functions - oct() — Python 3.9.1 documentation⁠

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Built-in Functions - hex() — Python 3.9.1 documentation⁠

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i = 255

print(bin(i))

print(oct(i))

print(hex(i))

# 0b11111111

# 0o377

# 0xff

print(type(bin(i)))

print(type(oct(i)))

print(type(hex(i)))

# <class 'str'>

source:

numeric_types.py⁠

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If you don't need the prefix, use slice [2:] to extract the trailing strings or use format() as described next.

⁠

How to slice a list, string, tuple in Python⁠

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print(bin(i)[2:])

print(oct(i)[2:])

print(hex(i)[2:])

# 11111111

# 377

# ff

source:

numeric_types.py⁠

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If you want to convert to a decimal string, use str().

⁠

Built-in Functions - str() — Python 3.9.1 documentation⁠

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print(str(i))

# 255

print(type(str(i)))

# <class 'str'>

source:

numeric_types.py⁠

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format(), str.format(), f-strings

The built-in function format(), the string method str.format(), and f-strings can also be used to convert a number to a binary, octal, and hexadecimal string.

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Built-in Functions - format() — Python 3.9.1 documentation⁠

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By specifying b, o and x in the format specification string of the second argument of format(), a number can be converted to a binary, octal, and hexadecimal string, respectively.

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string — Format Specification Mini-Language — Python 3.9.1 documentation⁠

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print(format(i, 'b'))

print(format(i, 'o'))

print(format(i, 'x'))

# 11111111

# 377

# ff

print(type(format(i, 'b')))

print(type(format(i, 'o')))

print(type(format(i, 'x')))

# <class 'str'>

source:

numeric_types.py⁠

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If you want to get the character string with the prefix 0b, 0o, 0x, add # to the format specification string.

print(format(i, '#b'))

print(format(i, '#o'))

print(format(i, '#x'))

# 0b11111111

# 0o377

# 0xff

source:

numeric_types.py⁠

⁠

It is also possible to fill in zero (0) with any number of digits. Note that the number of characters for the prefix (two characters) must also be taken into account when filling in zero with a prefix.

print(format(i, '08b'))

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