This post would have been more appropriate on python-list than
python-dev. But to answer your implied questions...
On 10/31/2012 3:57 PM, anatoly techtonik wrote:
Here is the code:
---[cut]-----------------------------
DEBUG = []
FONT_NAMES = []
This line has nothing to do with the behavior of the function that
follows. The error message would be the name if it were deleted.
def names():
if len(DEBUG):
print(len(DEBUG))
if len(FONT_NAMES):
print(len(FONT_NAMES))
if len(FONT_NAMES)==0:
FONT_NAMES = "query()"
This makes FONT_NAMES a local name *everywhere* within names.
names()
---[cut]-----------------------------
Here is the output:
Traceback (most recent call last):
File "globalocal.py", line 13, in <module>
names()
File "globalocal.py", line 8, in names
if len(FONT_NAMES):
UnboundLocalError: local variable 'FONT_NAMES' referenced before assignment
As you may see there is inconsistency between handling of line 6 -
"if len(DEBUG):" and line 8 - "if len(FONT_NAMES):".
No there is not.
This is very magical and hard to troubleshoot.
Names (not 'variables') within a function are deterministically
classified at compile time as local, nonlocal, or global according to
declarations and usage *within the function*. This classification has
nothing to do with names in other namespaces and is done independently
of other namespaces. The rules are described in the manuals.
I wonder if this message can be
improved with a pointer to the concept on when global variables become
local?
This never happens. Global names stay global (until deleted). They may
be masked by a local name with the same spelling (as in your example),
but that is a different issue.
--
Terry Jan Reedy
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