def main():
# compute the sum of the numbers
# entered by the user. The user stops
# by hitting the enter key.
sum = 0
# read first value
strInput = raw_input("enter 1st number (enter to quit):")
while strInput != "":
number = float(strInput)
sum += number
# read next value
strInput = raw_input("enter next number (enter to quit): ")
print "sum=", sum
main()