Best practice for paths - arcpy.env.workspace vs os.path.join

Question

Hi,

I've recently had an odd error and found it was due to the way I set up the input. The really odd thing is that some tools worked, but another (arcpy.CalculateStatistics_management) failed with the error:

Failed to execute. Parameters are not valid.
ERROR 000840: The value is not a Mosaic Dataset.
ERROR 000840: The value is not a Mosaic Layer.
ERROR 000840: The value is not a Raster Dataset.

Even though checking the input showed it to be valid raster dataset.

Here's the code that failed:arcpy.CalculateStatistics_management("demExtract","1","1","#","OVERWRITE")

If I put the full path, it worked. Seems that setting arcpy.env.workspace didn't work for this tool. Using this worked:arcpy.CalculateStatistics_management((os.path.join(gdbPath, "demExtract")),"1","1","#","OVERWRITE")

Is os.path.join something that should be used by default?

ClintonDow1 · Answer

Yes typically I would recommend getting used to PEP8 style, it is used for the majority of Python projects and is something that is appreciated during coding interviews 
 ArcPy actually breaks PEP8 in a lot of places for a number of historical reasons, so its not the best reference for the canonical Python style.

Edit: Late to the party. Oh well.

curtvprice · Answer

The biggest danger of using local path names I have run into is that they can conflict with layer names in your map. If you have a dataset named "foo" in your workspace and a layer named "foo" in your map (or in memory), the layer will be used. Took me a while to figure that one out.

DanPatterson_Retired · Answer

The key is, ... it is a guide ... not rules .... can't find the exact link, but even Python's BDFL said as much