tkinter Variable implementation
Hiya :) I'm recently working with tkinter and I noticed that:
import tkinter as tk string_var = tk.StringVar()
is throwing an AttributeError:
... 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
Actually, the error message should read something like this: A valid instance of Tk is required.
Could you file an issue about this on bugs.python.org <http://bugs.python.org/>? Ronald — Twitter / micro.blog: @ronaldoussoren Blog: https://blog.ronaldoussoren.net/
Actually, the error message should read something like this: A valid instance of Tk is required.
Could you file an issue about this on bugs.python.org <http://bugs.python.org/>? Ronald — Twitter / micro.blog: @ronaldoussoren Blog: https://blog.ronaldoussoren.net/
participants (3)
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Ivo Shipkaliev -
Ronald Oussoren -
William Pickard