Python bug? Named parameters in recursive calls sometimes confuses python?

[Magnus Lyck?]

Something really strange is happening to me (sometimes).
I'm using Python 2.3.2 on NT 4.0 as well as win32all-157,
adodbapi and db_row. 

During a recursive call to a method, it seems Python messes 
up its variable bindings once in a while. Suddenly, one of 
several local variables gets rebound to the object it was bound 
to one step up in the recursion. 

The relevant part of the code looks like this with print statements
that show the problem. This problem only seems to occur for certain
input to my program.

Note that I print the same variables and object IDs three times, and
suddenly, a variable has changed its binding (without any reassignment)
to the value it had one level up in the recursion.

    def recursiveCopy(self, table, column, old_val, new_val):
        # Fetch row from source database
        print "1. Column %s (%i) Table %s (%i)" % (column, id(column), 
                                                   table, id(table))

        sql = "SELECT * FROM %(schema)s.%(table)s WHERE %(column)s = ?"
        rows = self.src_fetch(sql, params=(old_val,), table=table,
                              column=column)
               # I use "sql % kwargs" in a method called by src_fetch

        print "2. Column %s (%i) Table %s (%i)" % (column, id(column), 
                                                   table, id(table))

        for row in rows:
            # Replace foreign key with value for target DB

            print "3. Column %s (%i) Table %s (%i)" % (column, id(column), 
                                                       table, id(table))

            row[column] = new_val  # <= This is where it crashes.
            # What's interesting is the print above before the crash.
            # row is a db_row.IMetaRow instance instance.

            # We need primary key values for recursive find
            # Only bother for table with a single p.k.
            parent_p_key_cols = self.getPK(table)
            if len(parent_p_key_cols) == 1:
                parent_p_key_col = parent_p_key_cols[0]
                oldId = row[parent_p_key_col]
                newId = self.insertIntoTarget(table, row)
                for child_table, column in self.getDepTables(table,
                                                             parent_p_key_col):
                    self.recursiveCopy(child_table, column, oldId, newId)

The output looks like this:

1. Column G06_PERS_INTRID (9282024) Table TGANST (9282768)
2. Column G06_PERS_INTRID (9282024) Table TGANST (9282768)
3. Column G06_PERS_INTRID (9282024) Table TGANST (9282768)
1. Column G60_ANSTID (9283512) Table TGANSTOV (10002536)
2. Column G60_ANSTID (9283512) Table TGANSTOV (10002536)
1. Column G08_ANSTID (10003232) Table TGANSTU (10002920)
2. Column G08_ANSTID (10003232) Table TGANSTU (10002920)
3. Column G08_ANSTID (10003232) Table TGANSTU (10002920)
1. Column G15_ANSTID (10002704) Table TGBELOPP (10003184)
2. Column G15_ANSTID (10002704) Table TGBELOPP (10003184)
1. Column G45_ANSTID (10002752) Table TGLED (9282672)
2. Column G45_ANSTID (10002752) Table TGLED (9282672)
1. Column G46_ANSTID (10002728) Table TGLON (10002512)
2. Column G46_ANSTID (10002728) Table TGLON (10002512)
3. Column G46_ANSTID (10002728) Table TGANST (9282768)  <= N.B. 
                                                  Table magically morphed.
Traceback (most recent call last):
  File "D:\NYPONVerktyg\Test\masterexport\get_person.py", line 364, in ?
    main()
  File "D:\NYPONVerktyg\Test\masterexport\get_person.py", line 336, in main
    move()
  File "D:\NYPONVerktyg\Test\masterexport\get_person.py", line 254, in move
    transfer.start(pnr)
  File "D:\NYPONVerktyg\Test\masterexport\get_person.py", line 181, in start
    self.recursiveCopy(table, column, old_pnr, new_pnr)
  File "D:\NYPONVerktyg\Test\masterexport\get_person.py", line 164, in recursiveCopy
    self.recursiveCopy(child_table, column, oldId, newId)
  File "D:\NYPONVerktyg\Test\masterexport\get_person.py", line 154, in recursiveCopy
    row[column] = new_val
  File "D:/NYPONVerktyg/Test/masterexport\db_row.py", line 526, in __setitem__
    self.fields.__setitem__(key,value)
  File "D:/NYPONVerktyg/Test/masterexport\db_row.py", line 370, in __setitem__
    setattr(self, i, value)
  File "D:/NYPONVerktyg/Test/masterexport\db_row.py", line 456, in __setattr__
    super(IFieldsBase, self).__setattr__(key.lower(),value)
AttributeError: 'irow_fields' object has no attribute 'g46_anstid'

Note that the 'table' variable (which is bound to a unicode object) changed
value from TGLON to TGANST and id from 10002512 to 9282768. I.e. we seem to
have jumped up one step in the stack. But the 'column' variable stayed 
unchanged, so we haven't popped the stack frame either!

Actually, it's even more weird. The table TGLON is empty, so self.src_fetch
ought to have returned an empty 'rows' variable, in which case we wouldn't
go into the loop, and would never see 'print "3. ...' Even though "print 2"
says TGLON, it seems TGANST is what got into the call of self.src_fetch,
and since DB2 didn't complain, it seems column actually have the value
G06_PERS_INTRID at that time (???). (Alternatively, we also reverted to
a previous rows-object?)

If I change the variable names to avoid "column=column" etc like this...

    def recursiveCopy(self, table_, column_, old_val, new_val):
        # Fetch row from source database
        print "1. Column %s (%i) Table %s (%i)" % (column_, id(column_), 
                                                   table_, id(table_))

        sql = "SELECT * FROM %(schema)s.%(table)s WHERE %(column)s = ?"
        rows = self.src_fetch(sql, params=(old_val,), table=table_,
                              column=column_)

...the problem seems to go away. (But it only occurred for some input
anyway. Maybe it just moved...)