Unexpected SyntaxError with decorators

Question

Here the goal is to call a global function as a decorator.

#coding: utf-8
def Test(method_to_decorate):
    print 'Decorator'
    def wrapper(self):
        return method_to_decorate(self)
    return wrapper


class Smth(object):
    def Test(self):
        print 'NOT a decorator!'

    a=globals()['Test']

    #@globals()['Test'] --> SyntaxError
    @a # works fine
    def Fun(self):
        print "Smth.Fun()"

l = Smth()
l.Fun()

Using the uncommented approach works fine while @globals()['Test'] gives SyntaxError. Why? I'm quite sure Test exists in globals().

The thing after @ must be a function accepting another function as one of its arguments, am I right? globals()['Test'] is such a function, isn't it? Then, in my opinion, @globals()['Test'] must be correct (logically correct).

Edit

This works as expected:

def Ex(*args):
    print 'Ex({})'.format(args) 
globals()['Ex']('hello') # just calling a function

While a decorator is used, a function is called. We can call functions as above but can't use a decorator like this. Maybe this is some sort of a Python bug or logic misorganisation?

Answer 1

It's a SyntaxError because Python's grammar explicitly does not allow that; the tokens on the right of @ are not an expression. 1 Instead, valid syntax is:

decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE

(A phrase enclosed in square brackets ([ ]) means zero or one occurrences (in other words, the enclosed phrase is optional).) 2

Following from the above, you can get this to work by converting globals()['Test'] to a dotted name. The following examples should work:

g = globals()
@g.get('Test')
def Fun(self):
    pass

x = globals()['Test']
@x
def Fun(self):
  pass

Or, as you noticed, you can just skip the syntactic sugar and decorate manually, which is probably the least bad option.