Coursera-Python learning Couse Exercises

#Assignment 5.2
#Finding the smallest and largest number
largest = None
smallest = None
while True:
    num = raw_input("Enter a number: ")
    if num == "done" : break
    try:
        #First input is given to both.
        if largest == None: largest = float(num)
        if smallest == None: smallest = float(num)
     
        #the smallest and largest changes with new inputs
        if smallest > float(num): smallest = float(num)
        if largest  < float(num): largest = float(num)
    except:
        print "Invalid input"
        continue
print "Maximum is", int(largest)
print "Minimum is", int(smallest)
c= raw_input("Enter to exit...")