[Python-Dev] Oddity in AST for 3-argument slices (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Thu Aug 19 12:35:34 CEST 2010

Nick Coghlan wrote:

Or else it's just an accident of implementation, since the AST doesn't actually need to distinguish those two cases.

It doesn't seem to be an accident, because ast_for_slice() goes out of its way to manufacture a Name node for the missing argument.

It doesn't seem to significantly simplify the compiler either, because compiler_slice() could just as easily treat it the same way as the other slice arguments and emit an instruction to load None if it's missing.

So it's a mystery. Perhaps it made life easier for some earlier version of the compiler.

-- Greg

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