I don't think PEP8 has an opinion on this either way; it's fairly specialized syntax for Numpy. The [Numpy manual](http://docs.scipy.org/doc/numpy/user/basics.indexing.html#structural-indexing-tools) explicitly uses this syntax with no spaces: see `z[1,:,:,2]`. Besides, as you say, this file is not PEP8-compliant to begin with (see the previous two lines).