numpy.binary_repr#

numpy.binary_repr(num, width=None)[source]#

Return the binary representation of the input number as a string.

For negative numbers, if width is not given, a minus sign is added to the front. If width is given, the two’s complement of the number is returned, with respect to that width.

In a two’s-complement system negative numbers are represented by the two’s complement of the absolute value. This is the most common method of representing signed integers on computers [1]. A N-bit two’s-complement system can represent every integer in the range \(-2^{N-1}\) to \(+2^{N-1}-1\).

Parameters:

numint: Only an integer decimal number can be used.
widthint, optional: The length of the returned string if num is positive, or the length of the two’s complement if num is negative, provided that width is at least a sufficient number of bits for num to be represented in the designated form. If the width value is insufficient, an error is raised.

Returns:

binstr: Binary representation of num or two’s complement of num.

See also

base_repr: Return a string representation of a number in the given base system.
bin: Python’s built-in binary representation generator of an integer.

Notes

binary_repr is equivalent to using base_repr with base 2, but about 25x faster.

References

[1]

Wikipedia, “Two’s complement”, https://en.wikipedia.org/wiki/Two’s_complement

Examples

>>> import numpy as np
>>> np.binary_repr(3)
'11'
>>> np.binary_repr(-3)
'-11'
>>> np.binary_repr(3, width=4)
'0011'

The two’s complement is returned when the input number is negative and width is specified:

>>> np.binary_repr(-3, width=3)
'101'
>>> np.binary_repr(-3, width=5)
'11101'