Prevent overriding Parameterized internal attributes?

[maximlt]

Parameterized classes and instances have attributes that users of those objects should not override, as doing so could break their code in hard-to-debug ways. Could/should ParameterizedMetaclass.__setattr__ be updated to raise a warning/error when the attribute name is one used by Param? This behavior should at least be documented.

Opening this issue was motivated by seeing the public initialized attribute on a Parameterized instance, which gave me goosebumps as I'm pretty sure I used that in some of my code. Fortunately it's planned to be updated to _initialized (#543).

import param
from pprint import pprint

class P(param.Parameterized):
    s = param.String()

pprint(P.__dict__)
print()
    
p = P(s='test')

pprint(p.__dict__)

EDIT: adding the output of the snippet above...

mappingproxy({'_P__params': {'name': <param.parameterized.String object at 0x1076ca040>,
                             's': <param.parameterized.String object at 0x10769af40>},
              '__doc__': 'params(s=String, name=String)\n'
                         "\x1b[1;32mParameters of 'P'\n"
                         '=================\n'
                         '\x1b[0m\n'
                         '\x1b[1;31mParameters changed from their default '
                         'values are marked in red.\x1b[0m\n'
                         '\x1b[1;36mSoft bound values are marked in '
                         'cyan.\x1b[0m\n'
                         'C/V= Constant/Variable, RO/RW = ReadOnly/ReadWrite, '
                         'AN=Allow None\n'
                         '\n'
                         '\x1b[1;34mNameValue  Type   Mode \x1b[0m\n'
                         '\n'
                         "s   ''  String  V RW \n"
                         '\n'
                         '\x1b[1;32mParameter docstrings:\n'
                         '=====================\x1b[0m\n'
                         '\n'
                         '\x1b[1;34ms: < No docstring available >\x1b[0m',
              '__module__': '__main__',
              '_param': <param.parameterized.Parameters object at 0x107651550>,
              '_parameters_state': {'BATCH_WATCH': False,
                                    'TRIGGER': False,
                                    'events': [],
                                    'watchers': []},
              'name': <param.parameterized.String object at 0x1076ca040>,
              's': <param.parameterized.String object at 0x10769af40>})

{'_dynamic_watchers': defaultdict(<class 'list'>, {}),
 '_instance__params': {},
 '_name_param_value': 'P00023',
 '_param_watchers': {},
 '_parameters_state': {'BATCH_WATCH': False,
                       'TRIGGER': False,
                       'events': [],
                       'watchers': []},
 '_s_param_value': 'test',
 'initialized': True}

[jlstevens]

Not sure it is a bug as such, just something you have to be aware of when using param.

That said, if it isn't too hard to help guard against such mistakes, then this is a good suggestion for an enhancement!

[jbednar]

Agreed, it would be nice to catch those.

[maximlt]

The Parameterized namespace being now reduced and documented after #766, I consider this issue resolved.