FloPy 3.3.5 Load model error "list index out of range"

[TIPJhonTellez]

thanks for reading. I am currently trying to load a MODFLOW6 simulation with the FloPy library and when migrating to version 3.3.5 I receive the following error "IndexError: list index out of range".

The next code run succesfully in FloPy version 3.3.4 like i write before makes and error the version 3.3.5

CODE:

#Importar librerias necesarias : OS y FloPy
import os
import sys
import flopy
from flopy.export import vtk
import numpy as np

print(sys.version)
print("flopy version: {}".format(flopy.__version__))

#Nombre del modelo
name = "2_Modelo2_grilla_k"
#Nombre del namefile
nam_file = "2_Modelo2_grilla_k.nam"
#Ruta de la ubicacion de la simulación
model_ws = os.getcwd()
#Ruta de los archivos a importar
model_output = os.path.join(model_ws, "VTKs")
#Ruta de MODFLOW
sim_path = "."

#Imprimimos los valores para verificar que sean correctos
print(model_ws, model_output, nam_file, name, sim_path)

#Carga la simulacion, en este caso los archivos de la simulacion generada por modflow o modelmuse
simulacion = flopy.mf6.MFSimulation.load(
    sim_name=name, exe_name="mf6", sim_ws="."
)

#Carga del modelo
modelo = simulacion.get_model()


print("simulación cargada")

The next code is the ERROR:

3.9.7 (default, Sep 16 2021, 16:59:28) [MSC v.1916 64 bit (AMD64)] flopy version: 3.3.5 
C:\Users\USUARIO\Downloads\Tutoriales Hidegatari\Modelmuse2\Modelmuse2 
C:\Users\USUARIO\Downloads\Tutoriales Hidegatari\Modelmuse2\Modelmuse2\VTKs 
2_Modelo2_grilla_k.nam 
2_Modelo2_grilla_k 
.

loading simulation...
  loading simulation name file...
  loading tdis package...
  loading model gwf6...
---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
Input In [4], in <cell line: 23>()
     20 print(model_ws, model_output, nam_file, name, sim_path)
     22 #Carga la simulacion, en este caso los archivos de la simulacion generada por modflow o modelmuse
---> 23 simulacion = flopy.mf6.MFSimulation.load(
     24     sim_name=name, exe_name="mf6", sim_ws="."
     25 )
     26 #simulacion = flopy.mf6.MFSimulation.load(sim_name=name, sim_ws=".")
     27 
     28 #Carga del modelo
     29 modelo = simulacion.get_model()

File ~\anaconda3\envs\Flopy335\lib\site-packages\flopy\mf6\modflow\mfsimulation.py:715, in MFSimulation.load(cls, sim_name, version, exe_name, sim_ws, strict, verbosity_level, load_only, verify_data, write_headers)
    713     if verbosity_level.value >= VerbosityLevel.normal.value:
    714         print(f"  loading model {item[0].lower()}...")
--> 715     instance._models[item[2]] = model_obj.load(
    716         instance,
    717         instance.structure.model_struct_objs[item[0].lower()],
    718         item[2],
    719         name_file,
    720         version,
    721         exe_name,
    722         strict,
    723         path,
    724         load_only,
    725     )
    727 # load exchange packages and dependent packages
    728 try:

File ~\anaconda3\envs\Flopy335\lib\site-packages\flopy\mf6\modflow\mfgwf.py:127, in ModflowGwf.load(cls, simulation, structure, modelname, model_nam_file, version, exe_name, strict, model_rel_path, load_only)
    114 @classmethod
    115 def load(
    116     cls,
   (...)
    125     load_only=None,
    126 ):
--> 127     return mfmodel.MFModel.load_base(
    128         simulation,
    129         structure,
    130         modelname,
    131         model_nam_file,
    132         "gwf",
    133         version,
    134         exe_name,
    135         strict,
    136         model_rel_path,
    137         load_only,
    138     )

File ~\anaconda3\envs\Flopy335\lib\site-packages\flopy\mf6\mfmodel.py:795, in MFModel.load_base(cls, simulation, structure, modelname, model_nam_file, mtype, version, exe_name, strict, model_rel_path, load_only)
    792 if model_rel_path and model_rel_path != ".":
    793     # strip off model relative path from the file path
    794     filemgr = simulation.simulation_data.mfpath
--> 795     fname = filemgr.strip_model_relative_path(modelname, fname)
    796 if (
    797     simulation.simulation_data.verbosity_level.value
    798     >= VerbosityLevel.normal.value
    799 ):
    800     print(f"    loading package {ftype}...")

File ~\anaconda3\envs\Flopy335\lib\site-packages\flopy\mf6\mfbase.py:288, in MFFileMgmt.strip_model_relative_path(self, model_name, path)
    286 new_path = ""
    287 for i, mrp in enumerate(model_rel_path_lst):
--> 288     if mrp != path_lst[i]:
    289         new_path = os.path.join(new_path, path_lst[i])
    290 for rp in path_lst[len(model_rel_path_lst) :]:

IndexError: list index out of range

[chris-nice-code]

I had a similar error message when opening a MODFLOW 6 Model that was prepared in Linux on a Windows machine. The NAM file used forward slashes as its path separator and FloPy was expecting the Windows separator (i.e. backslash). Knowing this made it easy to resolve the problem.

I would like to raise a bug for this and also offer to fix it. I can provide the steps to reproduce and the error message. What I don't know is what the correct behaviour would be.

When opening a model with forward slashes in the NAM file on a Windows machine? Should FloPy

1. interpret those paths recognising the forward slash as a path separator from another system, or
2. raise an exception indicating that the paths are invalid?

[wpbonelli]

Hi @TIPJhonTellez it would be helpful to see the contents of your namefile, as the error traces to code which parses the namefile for model input names/files. It would also be helpful to know if you see the same error with FloPy 3.3.6 or with the current development version 3.3.7 (can be installed with pip install git+https://github.com/modflowpy/flopy.git)

Thanks also @chris-nice-code, if you could provide steps to reproduce your version of the issue that would be great. As for correct behavior, I am still new so will defer here, but something like this seems reasonable:

• FloPy should successfully load regardless of separator if the path is an otherwise valid abs- or rel path or just filename
• Calling write_simulation() should write path separators suitable for the current OS
• If FloPy detects invalid path format at load time, maybe show a warning and suggest calling write_simulation() to correct the namefile/input file path separators to allow Modflow6 to run successfully? Since Modflow6 supports POSIX paths on all operating systems, the only invalid cases should be an absolute path with a drive letter on Windows, or Windows path separators on Mac or Linux.

This may already be the behavior we are aiming for, I'm not sure. In any case it seems worthwhile to explore with targeted tests. I took a step in this direction, including a tentative fix for similar IndexErrors, however there still seem to be a few issues on Windows. Feel free to take a look and build on what is there if you like.

Opened PR addressing IndexError on MFSimulation.load()