[Python-Dev] Switch statement (original) (raw)

M.-A. Lemburg mal at egenix.com
Mon Jun 12 19:30:55 CEST 2006

Thomas Lee wrote:

Hi all,

As the subject of this e-mail says, the attached patch adds a "switch" statement to the Python language. However, I've been reading through PEP 275 and it seems that the PEP calls for a new opcode - SWITCH - to be added to support the new construct. I got a bit lost as to why the SWITCH opcode is necessary for the implementation of the PEP. The reasoning seems to be improving performance, but I'm not sure how a new opcode could improve performance. Anybody care to take the time to explain this to me, perhaps within the context of my patch?

Could you upload your patch to SourceForge ? Then I could add it to the PEP.

Thomas wrote a patch which implemented the switch statement using an opcode. The reason was probably that switch works a lot like e.g. the for-loop which also opens a new block.

Could you explain how your patch works ?

BTW, I think this part doesn't belong into the patch:

Index: Lib/distutils/extension.py =================================================================== --- Lib/distutils/extension.py (revision 46818) +++ Lib/distutils/extension.py (working copy) @@ -185,31 +185,31 @@ continue

suffix = os.path.splitext(word)[1] - switch = word[0:2] ; value = word[2:] + switchword = word[0:2] ; value = word[2:]

-- Marc-Andre Lemburg eGenix.com

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