One way would be using a for loop:
def get_min_max(numbers):
if not all([type(number) in [int, float] for number in numbers]):
raise TypeError('All items in numbers must be int or float.')
min = None
max = None
for number in numbers:
min = number if min is None or number < min else min
max = number if max is None or number > max else max
return min, max