Assignment without global

Question

Accepted Answer

Assigning to count inside the function (count += 1 is count = count + 1) makes Python treat count as a local variable in that function. But count is read on the right-hand side before it has been assigned locally, which raises an UnboundLocalError. To modify the global count, you must declare global count at the top of the function. The tricky part is that Python decides at compile time whether a name is local - the presence of any assignment to count anywhere in the function body is enough to make it local.