#x = float(input("Enter a number:  "))
#print("Twice your number is: ", x*2)

# Works, but will crash with letters
#x = input("Enter a number:  ")
#if x == "":
#    print("Nothing entered, defaulting to 8.2")
#    x = 8.2
#else:
#    x = float(x)
#print("Twice your number is: ", x*2)

# Another way:  Catch the exception!
x = input("Enter a number:  ")
try:
    x = float(x)
except:
    print("Could not convert entry to float, using 8.2")
    x = 8.2
print("Twice your number is: ", x*2)