NameError assigning to class created in a function

[Duncan Booth]

[posted and mailed]

Andrew Bennetts <andrew-pythonlist at puzzling.org> wrote in 
news:mailman.1016603731.25922.python-list at python.org:

> So, it seems that you can't assign to a variable in a class if it has the
> same name as the variable you are assigning from.  Except that it works
> outside a function:
> 

It seems to be a problem with nested scopes. If a variable is assigned to 
anywhere in the class statement, then the local value is used after the 
assignment, but the global value is used before. If a variable is not 
assigned to then the nested scope rules apply.

   def f(y):
      class Private:
         x = y
         y = 42
      return Private
   f(33)

Comment out the assignment to y, and this works (Private.x gets 33 from y 
in nested scope), with the assignment to y in place this raises NameError. 
So far this is pretty much what I would have expected: you can use the 
value of y from the nested scope only if y is not a local variable in the 
class scope (although I would have expected an UnboundLocalError rather 
than a NameError).

But, if you assign a global variable y=77 then Private.x gets 77 which 
definitely seems wrong.

I knew before that nested scopes didn't seem to work quite the way I 
expected with classes, but this definitely looks like a bug. Either classes 
should not do nested scopes at all, or they should do them consistently 
with functions.

-- 
Duncan Booth                                             duncan at rcp.co.uk
int month(char *p){return(124864/((p[0]+p[1]-p[2]&0x1f)+1)%12)["\5\x8\3"
"\6\7\xb\1\x9\xa\2\0\4"];} // Who said my code was obscure?