Python runtime is configured incorrectly on Windows.

[IVLIVS-III]

@IVLIVS-III The example project still does not work after the fix. Here is the log:

Launching lib\main.dart on Windows in debug mode...
lib\main.dart:1
√  Built build\windows\runner\Debug\example.exe.
Connecting to VM Service at ws://127.0.0.1:50354/PgO4aU0b_qk=/ws
Could not find platform independent libraries <prefix>
Python path configuration:
  PYTHONHOME = (not set)
  PYTHONPATH = (not set)
  program name = 'python'
  isolated = 0
  environment = 1
  user site = 1
  safe_path = 0
  import site = 1
  is in build tree = 0
  stdlib dir = 'C:\Users\Anton\Documents\Flutter\dart_python_ffi\packages\python_ffi\example\Lib'
  sys._base_executable = 'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example\\build\\windows\\runner\\Debug\\example.exe'
  sys.base_prefix = 'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example'
  sys.base_exec_prefix = 'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example'
  sys.platlibdir = 'DLLs'
  sys.executable = 'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example\\build\\windows\\runner\\Debug\\example.exe'
  sys.prefix = 'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example'
  sys.exec_prefix = 'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example'
  sys.path = [
    'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example\\build\\windows\\runner\\Debug\\python311.zip',
    'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example',
    'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example\\Lib',
    'C:\\Users\\Anton\\Documents\\Flutter\\dart_python_ffi\\packages\\python_ffi\\example\\build\\windows\\runner\\Debug',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'
Current thread 0x00000bfc (most recent call first):
  <no Python frame>
Lost connection to device.
Exited (sigterm)

Originally posted by @pushkinman in #5 (comment)

[IVLIVS-III]

Hi @pushkinman, can you provide further steps to reproduce this issue?

On my system, the example project works fine. I did the following steps:

1. Check out the dart_python_ffi repo.
2. Install melos globally on your system via dart pub global activate melos
3. Run melos bs
4. Revert changes melos bs made to packages/python_ffi_cpython_dart/lib/src/ffi/generated_bindings.dart (no longer necessary after ec33eda)
5. Run the packages/python_ffi/example project
6. No issues, the flutter app launches fine

[pushkinman]

@IVLIVS-III after running melos bs i get the following errors

PS C:\Users\Anton\Documents\Flutter\dart_python_ffi> melos bs
melos bootstrap
  └> C:\Users\Anton\Documents\Flutter\dart_python_ffi

Running "flutter pub get" in workspace packages...
  ✓ lark
    └> packages/examples/lark
  ✓ python_ffi_lint
    └> packages/python_ffi_lint
  ✓ python_ffi_lint_dart
    └> packages/python_ffi_lint_dart
  ✓ basic_cli_adder
    └> packages/examples/basic_cli_adder
  ✓ scripts
    └> packages/python_ffi_cpython/scripts
  ✓ python_ffi_dart
    └> packages/python_ffi_dart
  ✓ dartpip_example
    └> packages/dartpip/example
  ✓ pytimeparse_dart
    └> packages/examples/pytimeparse_dart
  ✓ python_ffi_interface
    └> packages/python_ffi_interface
  ✓ python_ffi_cpython_dart
    └> packages/python_ffi_cpython_dart
  ✓ dartpip
    └> packages/dartpip
  ✓ python_ffi_dart_example
    └> packages/python_ffi_dart/example
  ✓ basic_dataclass
    └> packages/examples/basic_dataclass
  ✓ fj_playground
    └> packages/examples/fj_playground
  ✓ python_ffi_cpython
    └> packages/python_ffi_cpython
  ✓ python_ffi
    └> packages/python_ffi
  ✓ python_ffi_example
    └> packages/python_ffi/example
  > SUCCESS

Generating IntelliJ IDE files...
  > SUCCESS

 -> 17 packages bootstrapped

melos bootstrap [post]
  └> melos run ffigen

melos run ffigen
  └> melos exec -- "dart run ffigen
     melos run post_ffigen
     "
     └> RUNNING

$ melos exec
  └> dart run ffigen & C:\development\flutter/bin/internal/exit_with_errorlevel.bat
     └> RUNNING (in 1 packages)

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------python_ffi_cpython_dart:
Running in Directory: 'c:\Users\Anton\Documents\Flutter\dart_python_ffi\packages\python_ffi_cpython_dart'
[SEVERE] : Couldn't find dynamic library in default locations.
[SEVERE] : Please supply one or more path/to/llvm in ffigen's config under the key 'llvm-path'.
Unhandled exception:
Exception: Couldn't find dynamic library in default locations.
#0      findDylibAtDefaultLocations (package:ffigen/src/config_provider/spec_utils.dart:631:3)
#1      Config._getSpecs.<anonymous closure> (package:ffigen/src/config_provider/config.dart:261:29)
#2      Config._extract (package:ffigen/src/config_provider/config.dart:247:50)
#3      new Config.fromYaml (package:ffigen/src/config_provider/config.dart:194:17)
#4      getConfigFromPubspec (package:ffigen/src/executables/ffigen.dart:113:17)
#5      getConfig (package:ffigen/src/executables/ffigen.dart:80:14)
#6      main (package:ffigen/src/executables/ffigen.dart:48:14)
<asynchronous suspension>




---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
$ melos exec
  └> dart run ffigen & C:\development\flutter/bin/internal/exit_with_errorlevel.bat
     └> FAILED (in 1 packages)
        └> python_ffi_cpython_dart (with exit code 255)

melos run ffigen
  └> melos exec -- "dart run ffigen
     melos run post_ffigen
     "
     └> FAILED
ScriptException: The script ffigen failed to execute.

ScriptException: The script command/bootstrap/hooks/post failed to execute.

and then the exact same error as before when trying to start debuging on windows

[IVLIVS-III]

@pushkinman yep, I forgot that invoking package:ffigen requires llvm to be installed on your system.

However, we discard the output of ffigen anyways, see step 4:

4. Revert changes melos bs made to packages/python_ffi_cpython_dart/lib/src/ffi/generated_bindings.dart

This means, failing to run ffigen is not an issue… (I could decouple ffigen from bootstrap actually)

Anyways, I would have expected the app to run.

---

Which versions of Python did you install on your system and where are the install locations?

[pushkinman]

Python 3.11.4
C:\Users\Anton\AppData\Local\Microsoft\WindowsApps\python.exe

[IVLIVS-III]

Can you run the packages/examples/fj_playground example?

Sadly I cannot reproduce your issue with packages/python_ffi/example locally…

[pushkinman]

You are using a windows machine, right? (to test)

[IVLIVS-III]

You are using a windows machine, right? (to test)

Yes, to debug this issue I use a native Windows OS (no virtualization) on mac Intel hardware, i.e. natively booting directly into Windows.

[pushkinman]

I'm using bootcamp on Intel MacBook as well.

[pushkinman]

Can you run the packages/examples/fj_playground example?

Sadly I cannot reproduce your issue with packages/python_ffi/example locally…

It reproduces a similar error. Let me double check everything on my side, if you are saying that it works fine on your side, it should work for me as well.

[IVLIVS-III]

Yes, both work fine on my side…

[pushkinman]

Hello @IVLIVS-III, we've tested your example project as well as our own one, but we still get the same error. (We've tested on different Windows machines)

C:\Users\Pavel\dns-advisor-poc\ui>flutter run
Connected devices:
Windows (desktop) • windows • windows-x64    • Microsoft Windows [Version 10.0.19045.3086]
Chrome (web)      • chrome  • web-javascript • Google Chrome 114.0.5735.134
Edge (web)        • edge    • web-javascript • Microsoft Edge 114.0.1823.58
[1]: Windows (windows)
[2]: Chrome (chrome)
[3]: Edge (edge)
Please choose one (or "q" to quit): 1
Launching lib\main.dart on Windows in debug mode...
Building Windows application...                                   208.1s
√  Built build\windows\runner\Debug\dns_advisor_poc.exe.
Syncing files to device Windows...                               2,262ms

 

 

Flutter run key commands.
r Hot reload.
R Hot restart.
h List all available interactive commands.
d Detach (terminate "flutter run" but leave application running).
c Clear the screen
q Quit (terminate the application on the device).

 

 

A Dart VM Service on Windows is available at: http://127.0.0.1:49767/6rKNrlNPnx8=/
Could not find platform independent libraries <prefix>
Python path configuration:
  PYTHONHOME = (not set)
  PYTHONPATH = (not set)
  program name = 'python'
  isolated = 0
  environment = 1
  user site = 1
  safe_path = 0
  import site = 1
  is in build tree = 0
  stdlib dir = 'C:\Users\Pavel\dns-advisor-poc\ui\Lib'
  sys._base_executable = 'C:\\Users\\Pavel\\dns-advisor-poc\\ui\\build\\windows\\runner\\Debug\\dns_advisor_poc.exe'
  sys.base_prefix = 'C:\\Users\\Pavel\\dns-advisor-poc\\ui'
  sys.base_exec_prefix = 'C:\\Users\\Pavel\\dns-advisor-poc\\ui'
  sys.platlibdir = 'DLLs'
  sys.executable = 'C:\\Users\\Pavel\\dns-advisor-poc\\ui\\build\\windows\\runner\\Debug\\dns_advisor_poc.exe'
  sys.prefix = 'C:\\Users\\Pavel\\dns-advisor-poc\\ui'
  sys.exec_prefix = 'C:\\Users\\Pavel\\dns-advisor-poc\\ui'
  sys.path = [
   'C:\\Users\\Pavel\\dns-advisor-poc\\ui\\build\\windows\\runner\\Debug\\python311.zip',
   'C:\\Users\\Pavel\\dns-advisor-poc\\ui',
   'C:\\Users\\Pavel\\dns-advisor-poc\\ui\\Lib',
   'C:\\Users\\Pavel\\dns-advisor-poc\\ui\\build\\windows\\runner\\Debug',
  ]
Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

 

 

Current thread 0x0000120c (most recent call first):
<no Python frame>
The Flutter DevTools debugger and profiler on Windows is available at:
[http://127.0.0.1:9100?uri=http://127.0.0.1:49767/6rKNrlNPnx8=/](http://127.0.0.1:9100/?uri=http://127.0.0.1:49767/6rKNrlNPnx8=/)
Lost connection to device.

[maxim-saplin]

@IVLIVS-III I've tried running fj_playground example from master channel (as of yesterday) on Windows 11, when Python is installed, the app starts. When Python is removed the app doesn't work and fails with same error log as above:

Could not find platform independent libraries <prefix>
Python path configuration:
...

Python runtime and all dependencies are supposed to be bundled with the app and not depend on local installation of Python - is that right?