On Fri, Apr 15, 2016 at 10:40 AM, kirby urner <kirby.ur...@gmail.com> wrote:
>
> The increm function was originally looking in the global namespace for x...
>
That's not quite right either as this is simply wrong as a complete module:
x = 0
def createIncrementor(x):
def increm():
x = x + 1
return x
return increm
The "referenced before assignment" error will occur regardless of the
presence of a global x.
The choices to make increm work would be:
x = 100
def createIncrementor(x):
def increm():
global x
x = x + 1
return x
return increm
(a module is a kind of closure / enclosure -- coming in ES6 right?)
or:
def createIncrementor(x):
def increm():
nonlocal x
x = x + 1
return x
return increm
for an even more enclosed closure.
One may even remove x = from the module's global namespace and inject it
retroactively:
>>> from closure import createIncrementor
>>> inc = createIncrementor(5)
>>> inc()
Traceback (most recent call last):
File "<pyshell#80>", line 1, in <module>
inc()
File "/Users/kurner/Documents/classroom_labs/closure.py", line 4, in
increm
x = x + 1
NameError: global name 'x' is not defined
>>> x = 100 # this won't work either as '__main__' is not where it looks
>>> inc()
Traceback (most recent call last):
File "<pyshell#82>", line 1, in <module>
inc()
File "/Users/kurner/Documents/classroom_labs/closure.py", line 4, in
increm
x = x + 1
NameError: global name 'x' is not defined
>>> closure.x = 100 # this would work if I added closure to the namespace
Traceback (most recent call last):
File "<pyshell#83>", line 1, in <module>
closure.x = 100
NameError: name 'closure' is not defined
>>> import closure # which I do here
>>> closure.x = 100
>>> inc() # and now the earlier imported function works
with no problems
101
Kirby
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