def binary_search(alist, token):

'''function implements binary search algorithm using slicing

@author kgashok

@param alist is list of numbers to be searched

@param token is the number to be find in the list

@returns True if present, else False

>>> binary_search([0, 1, 2, 3, 4], 2)

True

'''

while alist:

mid = len(alist) // 2

midvalue = alist[mid]

if token is midvalue:

return True

if token < midvalue:

# for e.g. token is 3, and midvalue is 5

# throw/slice away the upper half

alist = alist[:mid]

else:

# if token is 7, and midvalue is 5

# throw/slice away the lower half

alist = alist[mid + 1:]

return False