Python error creating an instance of an object inside another
name-mangling, private-members, python
Solution
[moving my comment to an answer, as suggested]
This is the result of python's name mangling of "private" members. Rename from a double-underscore prefix to single-underscore, and problem is solved.
Problem
I'm creating a very simple container object in python and one of it's functions requires to create a temporary, null placeholder class that does absolutely nothing except tell the program what to delete. ``` class __cyclepass(object): "Null class as a placeholder for deleting items in a cycle.""" pass class Cycle(object): def __init__(self, *args): self.l = list(args) #......................... def __delitem__(self, key): """Magic method for deleting items via indexing.""" try: if isinstance(key, slice): s = key.start; e = key.stop; stp = key.step if key.step else 1 slicelen = abs((s - e) // stp) if slicelen == 1: steps = [s] else: steps = [s + stp * i for i in range(slicelen)] _list = copy(self.l) for step in steps: index = step % len(self) _list[index] = __cyclepass() #this is where an error occurs self.l = list(filter(lambda x: x.__class__ != __cyclepass, _list)) else: index = key % len(self) del self.l[index] except: raise IndexError("Bad index %s" % str(key)) ``` Everything seems fine (albeit a little bit messy but that is aside the point), but upon running the program and implicitly calling the delitem method I get this error: ``` NameError: global name '_Cycle__cyclepass' is not defined ``` What on earth would be causing it to look for `_Cycle__cyclepass` when creating the `__cyclepass` object?