find_previous_power_of_two.py

deffind_previous_power_of_two(number: int) ->int:
"""
 Find the largest power of two that is less than or equal to a given integer.
 https://stackoverflow.com/questions/1322510

 >>> [find_previous_power_of_two(i) for i in range(18)]
 [0, 1, 2, 2, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16, 16]
 >>> find_previous_power_of_two(-5)
 Traceback (most recent call last):
 ...
 ValueError: Input must be a non-negative integer
 >>> find_previous_power_of_two(10.5)
 Traceback (most recent call last):
 ...
 ValueError: Input must be a non-negative integer
 """
ifnotisinstance(number, int) ornumber<0:
raiseValueError("Input must be a non-negative integer")
ifnumber==0:
return0
power=1
whilepower<=number:
power<<=1# Equivalent to multiplying by 2
returnpower>>1ifnumber>1else1


if__name__=="__main__":
importdoctest

doctest.testmod()