Python Sugar

A really handy list comprehension technique that I am using heavily these days:

Instead of doing this:


for g in grGrps:
    gMeshes = self.meshesInGroup(g)
        if gMeshes:
            for m in gMeshes:
            # Append any meshes with lod0
            if re.search('_lod0', m.name()):
                eMeshes.append(m)

Do this:


for g in grGrps:
    for msh in [msh for msh in self.meshesInGroup(g) if self.meshesInGroup(g)]:
        # Append any meshes with lod0
        if re.search('_lod0', msh.name()):
            eMeshes.append(msh)

In the above case we are checking if the method returns anything, but the if portion is completely unrelated to the loop so it can be any if arg and/or/not appended to it. You could actually ADD ‘and re.search(‘_lod0’, msh.name()) to the if statement. Sometimes you may not want to go too crazy with the line length to keep things readable…

Another handy use is to filter file extensions when using os.walk:


for unused, unused, files in os.walk(os.path.abspath('yourPath')):
    for xml in [filename for filename in files if fnmatch(filename, '*.xml')]:
        #do something

In the last usage example, we are iterating through a list of attribute objects (pymel) and want to exclude attributes in an exclude list:


for sh in self.hlslShaders:
    for att in [att for att in sh.listAttr() if not att.name(includeNode=0) in excludes]:
        # Do Stuff

Having made the full MEL to Python transition at this point I am a much happier tools writer and I could never imagine going back. Whenever I have to revisit old MEL code, it is sort of painful. This particular syntax may be a given to a seasoned Python coder, but I just picked it up and find it incredibly useful.

Hoping to pass it along to anyone out there that is in a similar situation.

/Christian

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