Prerequirement

• Install PyCharm
• Install OSGeo4W Network Installer
  • choose QGIS desktop and QGIS full desktop

Setting the Environment

Create pygis.cmd

To setup the environment for PyQGIS in windows, you should get into the directory of ./OSGeo4W and create a pyqgis.cmd script. The following script is written by me according to the computer environment. Another to create a .cmd script is to get into the folder ./OSGeo4W/bin/python.bat and copy it to the main directory ./OSGeo4W. You should customize the set PATH statement to add any paths you want available when working from the command line. I added paths to my git install.

@echo off
    SET OSGEO4W_ROOT=D:\OSGeo4W64
    call "%OSGEO4W_ROOT%"\bin\o4w_env.bat
    call "%OSGEO4W_ROOT%"\apps\grass\grass-7.4.0\etc\env.bat
    @echo off
    path %PATH%;%OSGEO4W_ROOT%\apps\qgis\bin
    path %PATH%;%OSGEO4W_ROOT%\apps\grass\grass-7.4.0\lib
    path %PATH%;D:\OSGeo4W64\apps\Qt5\bin
    path %PATH%;D:\OSGeo4W64\apps\Python36\Scripts

    set PYTHONPATH=%PYTHONPATH%;%OSGEO4W_ROOT%\apps\qgis\python
    set PYTHONHOME=%OSGEO4W_ROOT%\apps\Python36

    set PATH=C:\Program Files\Git\bin;%PATH%

    cmd.exe

Through this .cmd, you can get into python3 and test if qgis can be imported. If you get errors when you import PyQt5.QtCore, don’t worry, we will fix in the next step.

C:\Users\gsherman>python3
    Python 3.6.0 (v3.6.0:41df79263a11, Dec 23 2016, 07:18:10) [MSC v.1900 32 bit (Intel)] on win32
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import qgis.core
    >>> import PyQt5.QtCore

Besides, you can install third packages through this command line script.

python3 -m pip install pandas
python3 -m pip install pb_tool

Create pycharm.cmd

By adding one line at the end of pyqgis.cmd, we can start IDE with recognising the QGIS libraries:

start "PyCharm aware of Quantum GIS" /B %PYCHARMPATH%

Please remember replace %PYCHARMPATH% as your own path where you installed PyCharm and save as new file pycharm.cmd. Within your IDE settings, point it to use the Python interpreter included with OSGeo4W—typically at: %OSGEO4W_ROOT%\bin\python3.exe. This will make it pick up all the QGIS goodies needed for development, completion, and debugging. Another important notice place here is that you should add QT_PLUGIN_PATH in this file.

set QT_PLUGIN_PATH=%OSGEO4W_ROOT%\apps\qgis\qtplugins;%OSGEO4W_ROOT%\apps\qt5\plugins

Here is the full script for pycharm.cmd, please note that my OSGEO4W_ROOT is C:\OSGeo4W64 and grass version is grass78 and python version is Python37.

@echo off
SET OSGEO4W_ROOT=D:\OSGeo4W64
call "%OSGEO4W_ROOT%"\bin\o4w_env.bat
call "%OSGEO4W_ROOT%"\bin\qt5_env.bat
call "%OSGEO4W_ROOT%"\bin\py3_env.bat
call "%OSGEO4W_ROOT%"\apps\grass\grass-7.4.0\etc\env.bat
@echo off
path %PATH%;%OSGEO4W_ROOT%\apps\qgis\bin
path %PATH%;%OSGEO4W_ROOT%\apps\grass\grass-7.4.0\lib
path %PATH%;D:\OSGeo4W64\apps\Qt5\bin
path %PATH%;D:\OSGeo4W64\apps\Python36\Scripts

set PYTHONPATH=%PYTHONPATH%;%OSGEO4W_ROOT%\apps\qgis\python
set PYTHONHOME=%OSGEO4W_ROOT%\apps\Python36
set QT_PLUGIN_PATH=%OSGEO4W_ROOT%\apps\qgis\qtplugins;%OSGEO4W_ROOT%\apps\qt5\plugins

start "PyCharm aware of QGIS" /B "C:\Program Files\JetBrains\PyCharm Community Edition 2017.2.3\bin\pycharm.exe"

Setting PyCharm IDE

Just double-click pycharm.cmd to start PyCharm. In the settings of PyCharm project, set interpreter as %OSGEO4W_ROOT%\bin\python3.exe. In my computer, the full path of interpreter is D:\OSGeo4W64\bin\python3.exe.

Reference

1. Error from create a reference to the QgsApplication

2. Quick Guide to Getting Started with PyQGIS 3 on Windows