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’scomplement 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 [R23]. A Nbit two’scomplement system can represent every integer in the range to .
Parameters:  num : int
width : int, optional


Returns:  bin : str

See also
Notes
binary_repr is equivalent to using base_repr with base 2, but about 25x faster.
References
[R23]  (1, 2) Wikipedia, “Two’s complement”, http://en.wikipedia.org/wiki/Two’s_complement 
Examples
>>> 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=4)
'1101'