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:
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
Actually, the error message should read something like this: A valid instance of Tk is required.
Thank you! On Sun, 13 Dec 2020 at 03:57, William Pickard <lollol222gg@gmail.com> wrote:
Actually, the error message should read something like this: A valid instance of Tk is required. _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-leave@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/EIEQ2P... Code of Conduct: http://python.org/psf/codeofconduct/
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/
On 13 Dec 2020, at 03:16, Ivo Shipkaliev <ivo.shipkaliev@gmail.com> wrote:
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-leave@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/FSQUFJ... Code of Conduct: http://python.org/psf/codeofconduct/
Yes, will do. Regards Ivo Shipkaliev On Sun, 13 Dec 2020 at 15:40, Ronald Oussoren <ronaldoussoren@mac.com> wrote:
Could you file an issue about this on bugs.python.org?
Ronald
—
Twitter / micro.blog: @ronaldoussoren Blog: https://blog.ronaldoussoren.net/
On 13 Dec 2020, at 03:16, Ivo Shipkaliev <ivo.shipkaliev@gmail.com> wrote:
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-leave@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/FSQUFJ... Code of Conduct: http://python.org/psf/codeofconduct/
participants (3)
-
Ivo Shipkaliev -
Ronald Oussoren -
William Pickard