[Question] I'm encountering a ModuleNotFoundError "wsgiref" when running my Flet app after building:

[ShibainuHacker]

Simple flet project but error occurs.

test_wsgiref.zip

Question

Error Title

ModuleNotFoundError: No module named 'wsgiref'

Environment

• OS: macOS Sonoma 14.5
• Flet version: 0.25.2
• Python version: 3.12.5

Steps to Reproduce

1. Building the Flet app using flet build macos --project myAppName --copyright myName --build-version 0.1.0
2. Running the built application
3. Error appears immediately on startup

Expected Behavior

The application should start normally without any module import errors.

Additional Context

• Using pygsheets for Google Sheets integration
• The application works fine in development mode
• The error only occurs in the built/packaged version

Questions

1. Is this a known issue with packaging Flet applications that use Google OAuth?
2. How can I ensure the wsgiref module is properly included in the built package?
3. Are there any workarounds or alternative approaches?

Code sample

from google.oauth2.credentials import Credentials
from google.oauth2 import service_account
from google.auth.transport.requests import Request
import pygsheets

Some Codes...

Error message

Traceback (most recent call last):
  File "<string>", line 47, in <module>
  File "<frozen runpy>", line 229, in run_module
  File "<frozen runpy>", line 88, in _run_code
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/main.py", line 4, in <module>
    from screen_settings import SettingsScreen
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/screen_settings.py", line 6, in <module>
    from service_config_checker import ServiceConfigChecker
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/service_config_checker.py", line 3, in <module>
    from service_sheet import ServiceSheet
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/service_sheet.py", line 4, in <module>
    import pygsheets
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/__pypackages__/pygsheets/__init__.py", line 14, in <module>
    from pygsheets.authorization import authorize
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/__pypackages__/pygsheets/authorization.py", line 8, in <module>
    from google_auth_oauthlib.flow import Flow, InstalledAppFlow
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/__pypackages__/google_auth_oauthlib/__init__.py", line 21, in <module>
    from .interactive import get_user_credentials
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/__pypackages__/google_auth_oauthlib/interactive.py", line 27, in <module>
    import google_auth_oauthlib.flow
  File "/Users/myAccount/Library/Application Support/com.mycompany.myAppName/flet/app/__pypackages__/google_auth_oauthlib/flow.py", line 62, in <module>
    import wsgiref.simple_server
ModuleNotFoundError: No module named 'wsgiref'

files

main.py

import flet as ft
from google.oauth2.credentials import Credentials
from google.oauth2 import service_account
from google.auth.transport.requests import Request
import pygsheets

def main(page: ft.Page):
    page.title = "Flet App with Side Menu"
    page.padding = 0
    page.theme_mode = "light"

    page.add(ft.Text("Hello, World!"))

ft.app(target=main)

pyproject.toml

[project]
name = "myAppName"
version = "0.1.0"
description = ""
readme = "README.md"
requires-python = ">=3.8"
dependencies = [
  "flet==0.25.2",
  "google-auth-oauthlib==1.1.0",
  "pygsheets==2.0.6",
]


[tool.flet]
# org name in reverse domain name notation, e.g. "com.mycompany".
# Combined with project.name to build bundle ID for iOS and Android apps
org = "com.mycompany"

# project display name that is used as an app title on Android and iOS home screens,
# shown in window titles and about app dialogs on desktop.
product = "myAppName"

# company name to display in about app dialogs
company = "Flet"

# copyright text to display in about app dialogs
copyright = "Copyright (C) 2024 by Flet"

[tool.flet.app]
path = "src"

------------------------------------------------------

• I have searched for answers to my question both in the issues and in previous discussions.

[baebranch]

Could be a hidden import causing the issue. I've had a similar issue on windows trying to build with Langchain libraries. Try adding the package to your requirements file, and even just importing it near the entry point of you application.

[ShibainuHacker]

@baebranch Thank you for you reply!
I understand what you're saying, but it seems a bit difficult for me to solve.
I've attached a simple flet project for debugging purposes.
Would you be able to try it out?

[baebranch]

I created an environment and installed the modules. Using flet build I got a different error message but using pyinstaller it worked fine.

[kentbull]

I hit this problem on Flet 0.27.1 and came across a workaround.

For some reason Flet's build process isn't recognizing wsgiref, so I copied the source code of wsgiref from the CPython repo folder here to a local folder in my app ("vendor/v_wsgiref"). I'll have an open source example soon to show.

In my local copy of wsgiref I add the following to its __init__.py

from . import handlers
from . import headers
from . import simple_server
from . import types
from . import util
from . import validate

all = ['handlers', 'headers', 'simple_server', 'types', 'util', 'validate']

and change one import in my v_wsgiref/simple_server.py to be the following:

from from wsgiref.handlers import SimpleHandler
to from .handlers import SimpleHandler
I use the relative import to cause it to avoid pulling the Python standard library version of wsgiref in because it triggers a ModuleNotFound error.

And then in my main.py I add the following:

import sys
from vendor import v_wsgiref
sys.modules["wsgiref"] = v_wsgiref

This workaround gets me a functional app, yet it is really weird why Flet would not include wsgiref by default.

It's really weird why this would be happening.