Error when creating Gtk.Box instance

[ljh]

Hi community,

Why the third call to create Box instance is wrong,
since Box.__init__() does not have keyword parameters?

Thanks

# box1 = Gtk.Box.new(Gtk.Orientation.HORIZONTAL, 5)
# box2 = Gtk.Box(    orientation=Gtk.Orientation.HORIZONTAL, spacing=5)
box3   = Gtk.Box(    Gtk.Orientation.HORIZONTAL, 5) # error

$ python3 hello.py
Traceback (most recent call last):
    box3 = Gtk.Box(Gtk.Orientation.HORIZONTAL, 5)
TypeError: GObject.__init__() takes exactly 0 arguments (2 given)
$ 

# /usr/local/lib/python3.10/site-packages/gi-stubs/repository/Gtk.pyi
class Box(Orientable, Container):
    def __init__(self, orientation: Optional[Orientation] = None, spacing: Optional[int] = None) -> None: ...
    def new(*args, **kwargs): ...

[ebassi (Emmanuele Bassi)]

I already told you: when using pygobject, the Python’s normal constructor form does not take positional arguments.

Every type that derives from GObject.Object has an automatic constructor for the type, which takes named arguments; those named arguments are any writable object property.

For more information, please read the pygobject documentation. Also: stop using the gi-stubs module. It’s clearly wrong.

[ljh]

Hi ebassi,

If named parameters are intended, can the Box.__init__ be written like
this?

class Box:

# def __init__(self, orientation: Optional[Orientation] = None, spacing: Optional[int] = None) -> None: ...

  def __init__(self, **kwarg):
    ...

# x = Box("H", 5) # error

  x = Box(orientation="H", spacing=5)

The non-named args will be caught earlier in Box class, not until
PyGObject class. But names and values pair can be checked in PyGObject.

The function definitions from PyGObject-stubs match the API document
from https://lazka.github.io/pgi-docs. If the stubs function
definitions are wrong, what about the pgi-docs? What can I get for
reference?

If I uninstall PyGObject-stubs, I can not get function and parameter
hints and suggestions for PyGObject functions in VSCode.

Thanks

[mazharhussain]

@ljh

If named parameters are intended, can the Box.__init__ be written like
this?

There is no Box.__init__() written in PyGObject. PyGObject uses introspection data to create objects. It would be extremely tedious work to explicitly write __init__() methods for each GObject Type. Explicitly written __init__() methods would also cause a lot of problems since the underlying GObject Type is bound to change. Properties, methods, constructors, etc. could be added, deprecated, or removed and PyGObject implementation of __init__() would have to be updated manually.

@ljh

The function definitions from PyGObject-stubs match the API document
from https://lazka.github.io/pgi-docs. If the stubs function
definitions are wrong, what about the pgi-docs? What can I get for
reference?

As far as I know, pgi-docs is not enough (or even required at all). I, personally, use the official documentation for C and PyGObject User Guide directly.

@ljh

If I uninstall PyGObject-stubs, I can not get function and parameter
hints and suggestions for PyGObject functions in VS Code.

Sorry, but that is, currently, how it is; No auto-completion/suggestions for GObject based libraries in Python.

At least that’s case on VS Code. I don’t know about the situation on GNOME Builder though. On it’s homepage it does say

Explore APIs used by your project with auto-completion for C/C++, Python, Rust, and Vala. For languages without native support, ctags integration is provided.

So, maybe GNOME Builder has what you need.

[ljh]

Thanks.

I’m trying tkinter. It contains enough information even in the document comment in its source code.