uTypeError: unsupported operand type(s) for -: 'str' and 'str'

Question

I get this error:

uTypeError: unsupported operand type(s) for -: \'str\' and \'str\'

From this code:

print \"wha         


        

Answer 1

raw_input() returns a string, so basically you end up with this:

print '20'-'11'

Since you cannot subtract one string from another, you need to convert them to numbers first.

Try this:

z = float(raw_input())
...
f = float(raw_input())

Secondly, use descriptive variable names instead of x, y, z and f, so something like:

age = float(raw_input())
...
firstPlaneTravelAge = float(raw_input())

print age-firstPlaneTravelAge, ...

Also note that this code has no validation, it will crash if the user enters something which isn't a number.

Answer 2

Your variables z and f are strings. Python doesn't support subtracting one string from another string.

If you want to display a number, you're going to have to convert them to either floats or integers:

print int(z) - int(f),"years ago",x, " first took an airplane."

The reason these are strings in the first place is because raw_input always returns a string.