OSError when starting Blender from the command line with '--python' option

[rlguy]

Blender Version: Blender 2.79
D-NOISE Version: 1.1.0 (DNOISE_v1_1_b2_79.zip)

Description

Hi Grant,

I had this issue reported to me by a user trying to run a FLIP Fluids simulation from the command line. Baking from the command line involves running Blender in the background with the '--background' option and loading a python script with the '--python' option. It looks like there is a conflict with D-NOISE that is causing Blender to produce an OSError which prevents the script from running.

How to Reproduce

I have constructed a minimal method of reproducing this error. Here is an example command run from the Windows PowerShell command line:

& 'C:\Program Files\Blender Foundation\Blender\blender.exe' --background --python python_script.py

I have attached the python script here: python_script.zip which just contains print statements:

print("Running python script...")
print("Python script finished.")

When launching Blender with the above command I get the following error:

OSError: Python file "C:\Users\ryanl\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\DNOISE\python_script.py" could not be opened: No such file or directory

Blender quit

The OSError causes Blender to terminate before running the script.

Possible Fix

I checked out the D-NOISE scripts and it looks like there are a few areas where os.chdir() is being used to change the python working directory. It seems this is causing a problem with the filepath when Blender tries to load the python_script.py file.

Specifically, the clean(directory, fileformat) method in fmutils.py seems to be causing the issue:

def clean(directory, fileformat):
    """Deletes all files of a given format from a directory"""
    os.chdir(directory)
    for file in os.listdir(directory):
        if fileformat in file:
            os.remove(file)

A possible fix is to save the current working directory into a variable and then reset the directory after the method is finished:

def clean(directory, fileformat):
    """Deletes all files of a given format from a directory"""
    original_directory = os.getcwd()
    os.chdir(directory)
    for file in os.listdir(directory):
        if fileformat in file:
            os.remove(file)
    os.chdir(original_directory)

After making this change, the script runs without errors:

Running python script...
Python script finished.

Blender quit

Workaround

This isn't a huge issue. A quick workaround is to disable the D-NOISE addon.

[TheDuckCow]

Just wanted to add in here, I really strongly hope that any and all change directory commands can be eliminated. As this error report indicated, there are many consequences. Is there a reason you can’t list the files using a relative or absolute path as the argument into listdir? I mean that from eg permissions or other blocking issue reason to do it that way. Also I’d recommend changing the logic from “fileformat in file” to “file.endswith(fileformat)” to further help eliminate any odd behavior and even perhaps further validating the file is indeed a file (and not a folder, which listdir also would return). As much as I’d hope users don’t have folders named ../MyFiles.png/, you never know 🙂

…

On Apr 2, 2019, at 17:11, Ryan Guy ***@***.***> wrote: Blender Version: Blender 2.79 D-NOISE Version: 1.1.0 (DNOISE_v1_1_b2_79.zip) Descriptions Hi Grant, I had this issue reported to me by a user trying to run a FLIP Fluids simulation from the command line. Baking from the command line involves running Blender in the background with the '--background' option and loading a python script with the '--python' option. It looks like there is a conflict with D-NOISE that is causing Blender to produce an OSError which prevents the script from running. How to Reproduce I have constructed a minimal method of reproducing this error. Here is an example command run from the Windows PowerShell command line: & 'C:\Program Files\Blender Foundation\Blender\blender.exe' --background --python python_script.py I have attached the python script here: python_script.zip which just contains print statements: print("Running python script...") print("Python script finished.") When launching Blender with the above command I get the following error: OSError: Python file "C:\Users\ryanl\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\DNOISE\python_script.py" could not be opened: No such file or directory Blender quit The OSError causes Blender to terminate before running the script. Possible Fix I checked out the D-NOISE scripts and it looks like there are a few areas where os.chdir() is being used to change the python working directory. It seems this is causing a problem with the filepath when Blender tries to load the python_script.py file. Specifically, the clean(directory, fileformat) method in fmutils.py seems to be causing the issue: def clean(directory, fileformat): """Deletes all files of a given format from a directory""" os.chdir(directory) for file in os.listdir(directory): if fileformat in file: os.remove(file) A possible fix is to save the current working directory into a variable and then reset the directory after the method is finished: def clean(directory, fileformat): """Deletes all files of a given format from a directory""" original_directory = os.getcwd() os.chdir(directory) for file in os.listdir(directory): if fileformat in file: os.remove(file) os.chdir(original_directory) After making this change, the script runs without errors: Running python script... Python script finished. Blender quit Workaround This isn't a huge issue. A quick workaround is to disable the D-NOISE addon. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.

[grantwilk]

I will fix this ASAP along with a lot of other changes that need to happen. Thank you for the heads up and for the detailed issue description!