Hiya :) I'm recently working with tkinter and I noticed that:
>>> import tkinter as tk >>> string_var = tk.StringVar() is throwing an AttributeError: > Traceback (most recent call last): > . . . > File "...\lib\tkinter\__init__.py", line 505, in __init__ > Variable.__init__(self, master, value, name) > File "...\lib\tkinter\__init__.py", line 335, in __init__ > self._root = master._root() > AttributeError: 'NoneType' object has no attribute '_root' ... which is making me question myself: -- "Why am I looking for a '_root' attribute on a NoneType object here?", or -- "How did I end up with a NoneType, to be searched for a '_root' attribute in the first place?" I have done something wrong or I don't know something apparently. Following the traceback, looking at "tkinter\__init__.py", lines 333-335 leads us to the implementation of StringVar's parent: class Variable: 333 > if not master: 334 > master = _default_root 335 > self._root = master._root() Class Variable constructor interface: 317 > def __init__(self, master=None, value=None, name=None): Clearly, on line 335, we are relying on the "master" to have a "_root" callable. If "master" was not declared upon class instantiation (line 317), a value can come from _default_root, which is a global module variable. _default_root is holding a Tk instance, if one was instantiated. So, if neither "master" nor _default_root was defined, line 335 will result in an AttributeError. Now, would it be a good idea if we keep the user better informed by making the aforementioned lines look something like?: 333 > if not master: 334 > master = _default_root 335 > if not master: 336 > raise RuntimeError(f"{self.__class__.__name__!r}: 'master' must be defined or a Tk instance must be present!") 337 > self._root = master._root() ... and not relying on this inexplicable AttributeError. Thank you for your time! Regards Ivo Shipkaliev
_______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/FSQUFJJQDNSRN4HI7VFXWCNO46YLXQDS/ Code of Conduct: http://python.org/psf/codeofconduct/