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