Here is my code:

```
def median(x):
sorted(x)
if len(x) % 2 != 0:
y = x[0:len(x) / 2 + 1]
z = y[len(y) - 1 : len(y)]
return sum(z)
else:
a = x[0:len(x) / 2 + 1]
b = a[len(a) - 1 : len(a)]
b = sum(b)
c = a[len(a) - 2 : len(a) - 1]
c = sum(c)
d = (b + c) / 2.0
return sum(d)
```

I get error message:

median([4, 5, 5, 4]) resulted in an error: ‘float’ object is not iterable

I have two questions: 1, how do I read this error message? what does is mean that something is not iterable? 2, I am using sum(b) to convert b from a list to an integer but this seems like a bad way. Is there a better way to do this?

Thanks!