The LSST Python Style guide which we base our style on balks at these kind of multi-clause one-line if/else statements: https://dev.lsstcorp.org/trac/wiki/PythonCodeStandards#MultipleStatementsSHOULDNOToccuronsameLine

PEP8 has the same (verbatim) instruction.  I think for the sake of compliance it's worth putting a space in these multi-clause statments.  Personally I don't find them so hard to read (I like the single line e.g. `if noise is not None: self.noise = noise`), but I don't care enough to make a specific exception to LSST/PEP8 style about it.