[Python] Why does a python script find the win32api - but not when run as a subprocess from...

I've got a script which when called via

(.venv) PS D:\Users\user4\MyPython\AllDiscs> py -m list_discs_with_folders dlist.txt


works as desired, but fails when called as a subprocess from another one:

import os
import time
from os.path import getmtime
import datetime
import sys

import win32api
from difflib import SequenceMatcher
import shutil


def get_drive_label(drive_path):
try:
volume_info = win32api.GetVolumeInformation(drive_path)
return volume_info[0] # name of the volume
except Exception as e:
print(f"Error: {e}")
return None
...


This codes works as expected (getting the volume information via win32api). But if i run the script from a second one:

import tkinter as tk
from tkinter import ttk, scrolledtext
import subprocess

root = tk.Tk()
root.title("Test WinAPI")

def build_sel():
subprocess.run(["python", "list_discs_with_folders.py", "dlist.txt"])

btn_run = ttk.Button(root, text="Build selected", command=build_sel)
btn_run.pack()

root.mainloop()


This gives an error:

Traceback (most recent call last):
File "D:\Users\user4\MyPython\AllDiscs\list_discs_with_folders.py", line 7, in <module>
import win32api
ModuleNotFoundError: No module named 'win32api'


Why does the interpreter find win32api in one case but not in the other?

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