Using relative path in WPF xaml file with pythonnet - python-3.x

Question

I am currently working on an application using WPF + pythonnet. And I encountered a problem of using relative path in the main xaml file to find the ResourceDictionary file. Here is a minimal example. There are three files in the app folder:
app/
|-main_window.py
|-main_window.xaml
|-resource.xaml
The main_window.py stores the python code that loads and shows the window layout from the xaml files:
import os
from pathlib import Path
import clr
clr.AddReference(r"wpf\PresentationFramework")
from System.Windows import Application
from System.IO import StreamReader
from System.Windows.Markup import XamlReader
from System.Threading import ApartmentState, Thread, ThreadStart
class MainWindow:
def __init__(self):
self.xamlFilePath = os.path.join(
Path(__file__).parent,
"main_window.xaml",
)
stream = StreamReader(self.xamlFilePath)
window = XamlReader.Load(stream.BaseStream)
Application().Run(window)
if __name__ == "__main__":
thread = Thread(ThreadStart(MainWindow))
thread.SetApartmentState(ApartmentState.STA)
thread.Start()
thread.Join()
The main_window.xaml file defines the layout of the application:
<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Height="200" Width="300">
<Window.Resources>
<ResourceDictionary>
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="./resource.xaml" />
</ResourceDictionary.MergedDictionaries>
</ResourceDictionary>
</Window.Resources>
<Grid>
<TextBlock>Test relative path for WPF + Pythonnet</TextBlock>
</Grid>
</Window>
And the resource.xaml stores the ResourceDictionary with the templates:
<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Style TargetType="TextBlock">
<Setter Property="Foreground" Value="Red" />
<Setter Property="HorizontalAlignment" Value="Center" />
<Setter Property="VerticalAlignment" Value="Center" />
</Style>
</ResourceDictionary>
Ideally, main_window.xaml should be able to find resource.xaml and load the Style tags. It works well if I provide absolute path, but for relative path it did not work. It gave an Exception: Python.Runtime.PythonException: XamlParseException
Interestingly, if I load the xaml file from Kaxaml, the resource.xaml can be found without problem.
Thanks in advance!