在Python中加载模块时出现意外行为

Question

As far as I understood, from module import * means that everything from the module will be locally available.

In my code I found:

from tkinter import *

and

from tkinter import filedialog

Looking back, I figured I could drop this last line, but then it is unavailable:

NameError: name 'filedialog' is not defined.

What am I missing?

Answer 1

From what I understand, Tkinter is a package (which means that it contains other modules). From Tkinter import * will only give you the default modules.

from the documentation:

6.4.1. Importing * From a Package

Now what happens when the user writes from sound.effects import *? Ideally, one would hope that this somehow goes out to the filesystem, finds which submodules are present in the package, and imports them all. This could take a long time and importing sub-modules might have unwanted side-effects that should only happen when the sub-module is explicitly imported.

The only solution is for the package author to provide an explicit index of the package. The import statement uses the following convention: if a package's init .py code defines a list named all , it is taken to be the list of module names that should be imported when from package import * is encountered. It is up to the package author to keep this list up-to-date when a new version of the package is released. Package authors may also decide not to support it, if they don't see a use for importing * from their package. For example, the file sounds/effects/ init .py could contain the following code:

Please, read the following post for another answer to your question. filedialog, tkinter and opening files