[Tutor] User input

[Danny Yoo]

> The second version works.
> 
> print "Total trip cost is US$", float(distance) /
> (float(mpg) * float(galon_price))

Hi Matt,

Although this works, we'll probably want to do the type conversions as 
early as possible.  We can write a function input_float() that wraps up 
the float(raw_input()) stuff:

###################################
def input_float(prompt):
     return float(raw_input(prompt))
###################################

If we have this as a helper function, then we don't have to worry about 
sprinkling float() conversions all over the place.