Solved!

In case this may be helpful to anyone, the solution for me was to declare an environment in subprocess.run:

env = os.environ.copy()
env["GDAL_DATA"] = "C:\\Program Files\\GDAL\\gdal-data"
env["PATH"] = (
            "C:\\GDAL"
            + os.pathsep
            + "C:\\Program Files\\GDAL"
            + os.pathsep
            + "C:\\Program Files\\TauDEM\\TauDEM5Exe")

Then either

subprocess.run([#mpiexecdir,"-n", "#ncores",#PitRemovedir, #DEMdir],shell=True,env=env,stdout=subprocess.PIPE,stderr=subprocess.PIPE,creationflags=subprocess.CREATE_NO_WINDOW)

or

subprocess.run([#PitRemovedir, #DEMdir],shell=True,env=env,stdout=subprocess.PIPE,stderr=subprocess.PIPE,creationflags=subprocess.CREATE_NO_WINDOW)

works well.

I had come across some similar solutions, but these did not work for me:

• https://stackoverflow.com/questions/33730231/qgis-python-script-returning-non-zero-exit-status-1
• Problem running shell command with PyQGIS

Furthermore, there is another plugin for QGIS 3 called "drainage" which can be handy. It performs all TauDEM processing as batch.

Cheers,

The solution for me was to declare an environment in subprocess.run:

env = os.environ.copy()
env["GDAL_DATA"] = "C:\\Program Files\\GDAL\\gdal-data"
env["PATH"] = (
            "C:\\GDAL"
            + os.pathsep
            + "C:\\Program Files\\GDAL"
            + os.pathsep
            + "C:\\Program Files\\TauDEM\\TauDEM5Exe")

Then either

subprocess.run([#mpiexecdir,"-n", "#ncores",#PitRemovedir, #DEMdir],shell=True,env=env,stdout=subprocess.PIPE,stderr=subprocess.PIPE,creationflags=subprocess.CREATE_NO_WINDOW)

or

subprocess.run([#PitRemovedir, #DEMdir],shell=True,env=env,stdout=subprocess.PIPE,stderr=subprocess.PIPE,creationflags=subprocess.CREATE_NO_WINDOW)

works well.

I had come across some similar solutions, but these did not work for me:

• https://stackoverflow.com/questions/33730231/qgis-python-script-returning-non-zero-exit-status-1
• Problem running shell command with PyQGIS

Furthermore, there is another plugin for QGIS 3 called "drainage" which can be handy. It performs all TauDEM processing as batch.