if L==[]:
    return (None, None)
min=max=L[0]
for x in L:
    if max<=x:
        max=x
    if min>=x:
        min=x        
return (min, max)

print(findMinAndMax([])) print(findMinAndMax([7])) print(findMinAndMax([7, 1])) print(findMinAndMax([7, 1, 3, 9, 5]))