The loop prints the smallest number as the largest

Question

I'm trying to find the smallest and largest numbers, but the output of the program is incorrect. The smallest is the largest in the output and the largest is always 1 smaller than the largest. I entered 2, 4, 6, 8, heres the output:

Enter a number: 2
Enter a number: 4
Enter a number: 6
Enter a number: 8
Enter a number: done
('largest is', 7)
('smallest is', 8)

And here's the code:

largest = None
smallest = None

while True:

    num = raw_input("Enter a number: ")

    if num == "done" : break
    try:
        halo = int(num)
    except:
        print("invalid input")
        continue
    for largest in range(halo):
        if largest is None:
            largest = halo
        elif largest > halo:
            largest = halo
    for smallest in range(halo):
        if smallest is None:
            smallest = halo
        elif smallest<halo:
            smallest = halo
print "largest is",largest
print "smallest is",smallest

Answer 1

You are always assigning a value to largest and smallest because you use them as targets in a for loop:

for largest in range(halo):

In the above, largest will be assigned 0 , then 1 , then 2 all the way up to the last number for halo .

Next, you have your < and > comparisons the wrong way around; you are only updating largest if halo is smaller . Invert your tests.

You don't need any loops at all here, your while True loop is your looping construct. Just test halo directly against largest and smallest :

try:
    halo = int(num)
except:
    print("invalid input")
    continue
if largest is None or halo > largest:
    largest = halo
if smallest is None or halo < smallest:
    smallest = halo