EXE Web API by Python

Introduction

From time to time, we may be asked to meet all of the following:

I want to incorporate AI made with Python into a Windows application
I want the AI interface to be a Web API
I don't want to communicate with the remote server
I don't want to install Python on the production terminal

I think there are various ways, but

Allow AI functionality to be exposed as a Web API in Python's web framework
Convert the Python script to an EXE file and bundle it with the application itself,
You can achieve this by running the EXE from the app itself.

This time we will use:

OS：Windows 10
Python: 3.7.7 (installed only in the development environment)
Web framework: Flask
EXE conversion: PyInstaller

(By the way, with FastAPI x uvicorn, there was a problem as of March 30, 2020. [https://github.com/pyinstaller/pyinstaller/pull/4664](https://github.com/pyinstaller/pyinstaller/ pull / 4664)))

procedure

Install Flask and PyInstaller.

At the command prompt etc.

pip install flask pyinstaller

Create a Python file that exposes the Web API.

`main.py`


from flask import Flask
app = Flask(__name__)

@app.route('/predict')
def predict():
  """
Intention of API to return prediction by AI
  """
  return {'result': 'Prediction by AI.'}

if __name__ == '__main__':
  app.run()

Move to the directory containing the above files and

pyinstaller main.py --onefile

There is main.exe in the dist directory, so let's try it.

dist\main.exe

Traceback (most recent call last):
  File "site-packages\PyInstaller\loader\rthooks\pyi_rth_pkgres.py", line 13, in <module>
  File "c:\users\user\appdata\local\programs\python\python37\lib\site-packages\PyInstaller\loader\pyimod03_importers.py", line 623, in exec_module
    exec(bytecode, module.__dict__)
  File "site-packages\pkg_resources\__init__.py", line 86, in <module>
ModuleNotFoundError: No module named 'pkg_resources.py2_warn'
[24508] Failed to execute script pyi_rth_pkgres

If you get ModuleNotFoundError as above, edit the main.spec file generated in the same hierarchy as main.py with a text editor. Specifically, include the module name that was not found in hiddenimports.

`main.spec`


             # --Abbreviation--
             hiddenimports=[],
             # --Abbreviation--

↓ Modify and save as follows.

`main.spec`


             # --Abbreviation--
             hiddenimports=['pkg_resources.py2_warn'],
             # --Abbreviation--

Run pyinstaller with the modified spec file instead of the py file.

pyinstaller main.spec --onefile

Check the operation again.

dist\main.exe

When you access it, you can roughly confirm that the Web API is open.

Actually, this EXE is executed from an application such as C # (process management required), and it will be accessed by the Http client from the same application.