Default interpreter Path does not respect .bat file when executing scripts

[maxgerhardt-phy]

Type: Bug

Behaviour

When declaring that the default Python interpeter is a .bat file (and switching to that environment), VSCode seems to pick up Intellisense correctly but when using Ctrl + Shift + P -> Run Python File in terminal, it uses an "evaluated" path to the python.exe file instead of the .bat file.

However, because the .bat file is setting up crucial environment variables, using the direct python.exe path fails to run any scripts at all.

This is critical when trying to run Python scripts meant for QGIS' python version.

Steps to reproduce:

1. Install QGIS (3.40 LTR) (https://qgis.org/download/)
2. You should now have C:/Program Files/QGIS 3.40.7/bin/python-qgis-ltr.bat
3. Create a new folder, open it in VSCode, create the .vscode/settings.json file as

{
    "python.defaultInterpreterPath": "C:/Program Files/QGIS 3.40.7/bin/python-qgis-ltr.bat"
}

4. Create a file minimal_init.py

from qgis.core import QgsApplication

QgsApplication.setPrefixPath("C:\\Program Files\\QGIS 3.40.7\\apps")
qgs = QgsApplication([], GUIenabled=False)
qgs.initQgis()
print("QGIS init OK")
qgs.exitQgis()

5. Try to run the script via Ctrl+Shift+P -> Run Python File in Terminal
6. Observe failed output

> & "C:/Program Files/QGIS 3.40.7/bin/python.exe" "c:/Users/Max Gerhardt/temp/xxxxxxxx/minimal_init.py"
Traceback (most recent call last):
  File "c:\Users\Max Gerhardt\temp\xxxxxxxx\minimal_init.py", line 1, in <module>
    from qgis.core import QgsApplication
ModuleNotFoundError: No module named 'qgis'

7. Observe expected output if using the .bat file correctly

> & 'C:\Program Files\QGIS 3.40.7\bin\python-qgis-ltr.bat' .\minimal_init.py
QGIS init OK

Diagnostic data

Output for Python in the Output panel (View→Output, change the drop-down the upper-right of the Output panel to Python)

2025-06-12 16:21:51.478 [info] Send text to terminal: & "C:/Program Files/QGIS 3.40.7/bin/python.exe" "c:/Users/Max Gerhardt/temp/xxxxxxxxxxxxxxxx/webserver.py"
2025-06-12 16:27:08.606 [info] Experiment 'pythonaa' is active
2025-06-12 16:27:08.606 [info] Experiment 'pythonRecommendTensorboardExt' is active
2025-06-12 16:27:08.606 [info] Experiment 'pythonTerminalEnvVarActivation' is active
2025-06-12 16:27:08.607 [info] Native locator: Refresh started
2025-06-12 16:27:08.607 [info] Native locator: Refresh started
2025-06-12 16:27:10.242 [info] > pyenv which python
2025-06-12 16:27:10.242 [info] cwd: c:\Users\Max Gerhardt\temp\xxxxxxxxxxxxxxxx
2025-06-12 16:27:11.026 [info] Python interpreter path: C:\Program Files\QGIS 3.40.7\bin\python.exe
2025-06-12 16:27:11.229 [info] Native locator: Refresh finished in 2830 ms
2025-06-12 16:27:13.470 [info] Starting Pylance language server.
2025-06-12 16:27:14.580 [error] Active interpreter type is detected as Unknown {"id":"C:\\Program Files\\QGIS 3.40.7\\bin\\python.exe","sysPrefix":"C:\\Program Files\\QGIS 3.40.7\\apps\\Python312","envType":"Unknown","envName":"","envPath":"C:\\Program Files\\QGIS 3.40.7\\bin\\python.exe","path":"C:\\Program Files\\QGIS 3.40.7\\bin\\python.exe","architecture":3,"sysVersion":"","version":{"raw":"3.12.10","major":3,"minor":12,"patch":10,"build":[],"prerelease":[]},"displayName":"Python 3.12.10","detailedDisplayName":"Python 3.12.10"}
2025-06-12 16:46:12.096 [info] Discover tests for workspace name: xxxxxxxxxxxxxxxx - uri: c:\Users\Max Gerhardt\temp\xxxxxxxxxxxxxxxx\minimal_init.py
2025-06-12 16:46:16.580 [info] Send text to terminal: & "C:/Program Files/QGIS 3.40.7/bin/python.exe" "c:/Users/Max Gerhardt/temp/xxxxxxxxxxxxxxxx/minimal_init.py"
2025-06-12 16:46:49.909 [info] Discover tests for workspace name: xxxxxxxxxxxxxxxx - uri: c:\Users\Max Gerhardt\temp\xxxxxxxxxxxxxxxx\minimal_init.py
2025-06-12 16:46:51.530 [info] Discover tests for workspace name: xxxxxxxxxxxxxxxx - uri: c:\Users\Max Gerhardt\temp\xxxxxxxxxxxxxxxx\minimal_init.py

Extension version: 2025.6.1
VS Code version: Code 1.100.3 (258e40fedc6cb8edf399a463ce3a9d32e7e1f6f3, 2025-06-02T13:30:54.273Z)
OS version: Windows_NT x64 10.0.19045
Modes:

• Python version (& distribution if applicable, e.g. Anaconda): 3.12.10
• Type of virtual environment used (e.g. conda, venv, virtualenv, etc.): Unknown
• Value of the python.languageServer setting: Default

User Settings

envFile: "<placeholder>"

languageServer: "Pylance"

Installed Extensions

Extension Name	Extension Id	Version
cpptools	ms-	1.25.3
debugpy	ms-	2025.8.0
hexeditor	ms-	1.11.1
js-debug	ms-	1.100.1
js-debug-companion	ms-	1.1.3
platformio-ide	pla	3.3.4
python	ms-	2025.6.1
vscode-js-profile-table	ms-	1.0.10
vscode-pylance	ms-	2025.5.1

System Info

Item	Value
CPUs	AMD Ryzen 7 PRO 5850U with Radeon Graphics (16 x 1896)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	59.83GB (25.04GB free)
Process Argv	--crash-reporter-id f4192565-3aa4-4705-8793-f5cca82f9e4f
Screen Reader	no
VM	50%

A/B Experiments

vsliv368:30146709
vspor879:30202332
vspor708:30202333
vspor363:30204092
vscod805:30301674
binariesv615:30325510
vscaac:30438847
c4g48928:30535728
azure-dev_surveyone:30548225
vscrp:30673768
2i9eh265:30646982
962ge761:30959799
2e7ec940:31000449
pythontbext0:30879054
cppperfnew:31000557
dwnewjupyter:31046869
pythonrstrctxt:31112756
nativeloc1:31192215
5fd0e150:31155592
dwcopilot:31170013
6074i472:31201624
dwoutputs:31242946
customenabled:31248079
9064b325:31222308
copilot_t_ci:31222730
e5gg6876:31282496
pythoneinst12:31285622
bgtreat:31268568
4gafe986:31271826
c7cif404:31314491
pythonpulldiagcf:31325931
996jf627:31283433
pythonrdcb7:31303018
usemplatestapi:31297334
0aa6g176:31307128
7bj51361:31289155
747dc170:31275177
6518g693:31325878
pylancecolor:31314202
aj953862:31281341
generatesymbolt:31295002
convertfstringf:31295003
gendocf:31295004

[maxgerhardt-phy]

By coincidence when working on another issue, I found out that placing

{
    "python.locator": "js"
}

in my VSCode user config resolves that issue, but it can't be done per-project (in the .vscode/settings.json) file. It would be good if the default Python locator handles pointing it to bat files correctly?

[eleanorjboyd]

Hello! To make sure I understand where the bug comes in, the path you are setting for "python.defaultInterpreterPath": "C:/Program Files/QGIS 3.40.7/bin/python-qgis-ltr.bat" is not being used (instead it is using "C:/Program Files/QGIS 3.40.7/bin/python.exe" right?

[maxgerhardt-phy]

Exactly. The python-qgis-ltr.bat first sets up some critical environment variables (like PYTHONHOME, PYTHONPATH, PATH, O4W_QT_LIBRARIES, ..), and then forwards all arguments to the actual python.exe inside QGIS. VSCode with the default python.locator seems to try to evaluate the actual Python interpreter path, bypassing the (critically needed) environment variable setup.