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Nov 6, 2009, 11:23 AM
Post #1 of 4
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[issue7276] UnboundLocalError scoping problem with nested functions
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New submission from Ole Laursen <olau [at] iola>:
This works:
def outer(name):
tmp = name
def inner():
print(tmp)
return inner
outer("foo") # prints "foo"
While the same code with one extra line (setting tmp after printing)
fails
def outer(name):
tmp = name
def inner():
print(tmp)
tmp = "hello"
return inner
outer("foo")()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 4, in inner
UnboundLocalError: local variable 'tmp' referenced before assignment
and the following works
def outer(name):
tmp = name
def inner():
tmp = "hello"
print(tmp)
return inner
outer("foo")() # prints "hello"
Now, I understand there's an interesting issue of assignment binding to
the inner-most scope. So tmp = "hello" is binding a new variable, not
changing the outermost tmp. But I should still be able to read tmp,
right? It looks like some kind of optimizer error.
For the record, this pattern came up in a decorator like this
def deco(x = None):
def inner(fn):
if not x:
x = somedefaultvalue
return inner
which gives the same UnboundLocalError error.
----------
messages: 94994
nosy: olau
severity: normal
status: open
title: UnboundLocalError scoping problem with nested functions
type: compile error
_______________________________________
Python tracker <report [at] bugs>
<http://bugs.python.org/issue7276>
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