[Python-Dev] Syntax suggestion for imports (original) (raw)

Ron Adam rrr at ronadam.com
Thu Jan 3 18:48:28 CET 2008

Raymond Hettinger wrote:

The standard library, my personal code, third-party packages, and my employer's code base are filled with examples of the following pattern:

try: import threading except ImportError: import dummythreading as threading try: import xml.etree.cElementTree as ET except ImportError: try: import cElementTree as ET except ImportError: import elementtree.ElementTree as ET try: from cStringIO import StringIO except ImportError: from StringIO import StringIO try: import readline except ImportError: pass

How about a new, simpler syntax: * import threading or dummythreading as threading * import xml.etree.CElementTree or cElementTree or elementree.ElementTree as ET * from cStringIO or StringIO import StringIO * import readline or emptymodule

I don't think it's as visually clear, but that may be I'm just not used to it.

An alternative possibility might be, rather than "or", reuse "else" before import.

import threading else import dummy_threading as threading

import xml.etree.CElementTree as ET else import cElementTree as ET else import elementtree.ElementTree as ET

The readline example above should be in a try except as it allows a failure to pass. For example if you wanted to allow the above elementtree example to pass instead of raising an exception you would write..

try: import xml.etree.CElementTree as ET else import cElementTree as ET else import elementtree.ElementTree as ET except ImportError: pass # or handle failed import.

This still improves readability and flattens out the multiple nested structure which I believe is what makes the current way unappealing.

I think multiple possible imports in "from - import"s statements should not be allowed. When you consider multiple imports from possibly multiple sources, it seems like that could get a bit messy when debugging.

Regards, Ron

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