import sys
import os
if hasattr(sys, 'frozen'):
 os.environ['PATH'] = sys._MEIPASS + ";" + os.environ['PATH']

from PyQt5.QtWidgets import QApplication, QMainWindow
from pyqt_ui.MainWindow import MainWin

if __name__ == '__main__':
 app = QApplication(sys.argv)
 mainWindow = QMainWindow()
 main_dialog = MainWin(mainWindow)
 mainWindow.show()
 sys.exit(app.exec_())

pyinstaller -F main2.py
INFO: PyInstaller: 3.5
INFO: Python: 3.6.4
INFO: Platform: Windows-7-6.1.7601-SP1
INFO: wrote E:\workspace\devTest\main2.spec
INFO: UPX is not available.
INFO: Extending PYTHONPATH with paths
['E:\\workspace\\devTest', 'E:\\workspace\\devTest']
INFO: checking Analysis
INFO: Building because E:\workspace\devTest\main2.py changed
INFO: Initializing module dependency graph...
INFO: Initializing module graph hooks...
INFO: Analyzing base_library.zip ...
INFO: running Analysis Analysis-00.toc
INFO: Adding Microsoft.Windows.Common-Controls to dependent assemblies of final executable
 required by d:\mytool\env\env36-32\scripts\python.exe
INFO: Caching module hooks...
INFO: Analyzing E:\workspace\devTest\main2.py
INFO: Processing pre-find module path hook distutils
INFO: distutils: retargeting to non-venv dir 'C:\\Program Files (x86)\\Python36-32\\Lib\\distutils\\__init__.py'
INFO: Processing pre-safe import module hook win32com
INFO: Loading module hooks...
INFO: Loading module hook "hook-encodings.py"...
INFO: Loading module hook "hook-pydoc.py"...
INFO: Loading module hook "hook-PyQt5.py"...
WARNING: Hidden import "sip" not found!
INFO: Loading module hook "hook-PyQt5.QtCore.py"...
INFO: Loading module hook "hook-PyQt5.QtGui.py"...
INFO: Loading module hook "hook-PyQt5.QtWidgets.py"...
INFO: Loading module hook "hook-pythoncom.py"...
INFO: Loading module hook "hook-pywintypes.py"...
INFO: Loading module hook "hook-win32com.py"...
INFO: Loading module hook "hook-xml.py"...
INFO: Looking for ctypes DLLs
INFO: Analyzing run-time hooks ...
INFO: Including run-time hook 'pyi_rth_pyqt5.py'
INFO: Including run-time hook 'pyi_rth_win32comgenpy.py'
INFO: Looking for dynamic libraries
INFO: Looking for eggs
INFO: Using Python library d:\mytool\env\env36-32\scripts\python36.dll
INFO: Found binding redirects:
[]
INFO: Warnings written to E:\workspace\devTest\build\main2\warn-main2.txt
INFO: Graph cross-reference written to E:\workspace\devTest\build\main2\xref-main2.html
INFO: checking PYZ
INFO: Building because toc changed
INFO: Building PYZ (ZlibArchive) E:\workspace\devTest\build\main2\PYZ-00.pyz
INFO: Building PYZ (ZlibArchive) E:\workspace\devTest\build\main2\PYZ-00.pyz completed successfully.
INFO: checking PKG
INFO: Building because toc changed
INFO: Building PKG (CArchive) PKG-00.pkg
WARNING: One binary added with two internal names.
WARNING: ('libGLESv2.dll',
 'D:\\mytool\\env\\env36-32\\lib\\site-packages\\PyQt5\\Qt\\bin\\libGLESv2.dll',
 'BINARY')
WARNING: was placed previously at
WARNING: ('PyQt5\\Qt\\bin\\libGLESv2.dll',
 'D:\\mytool\\env\\env36-32\\lib\\site-packages\\PyQt5\\Qt\\bin\\libGLESv2.dll',
 'BINARY')
INFO: Building PKG (CArchive) PKG-00.pkg completed successfully.
INFO: Bootloader d:\mytool\env\env36-32\lib\site-packages\PyInstaller\bootloader\Windows-32bit\run.exe
INFO: checking EXE
INFO: Building because toc changed
INFO: Building EXE from EXE-00.toc
INFO: Appending archive to EXE E:\workspace\devTest\dist\main2.exe
INFO: Building EXE from EXE-00.toc completed successfully.