[Python-ideas] csv.DictReader could handle headers more intelligently. (original) (raw)

J. Cliff Dyer jcd at sdf.lonestar.org
Wed Jan 23 22:13:54 CET 2013

On Wed, 2013-01-23 at 14:59 -0500, Jerry Hill wrote:

> However, since python is mechanising this as a dictionary and since in python > setting A to 1 then setting A to 3 would throw away the earlier value for A > and the import function working AS EXPECTED in Python.

I'm not sure this behavior merits the all-caps "AS EXPECTED" label. It's not terribly surprising once you sit down and think about it, but it's certainly at least a little unexpected to me that data is being thrown away with no notice. It's unusual for errors to pass silently in python.

Moreover, I think while it might be expected for a dict to do this, it does not follow that a DictReader should be expected to silently throw away the user's data. Just because it uses the dict format for storage does not mean that it's okay to throw away user's data silently. Dicts need to be blazingly fast for a host of reasons. DictReaders do not. They're usually dealing with file input, so any slowness in the DictReader itself is going to be dwarfed by the file access. As such we can afford to be more programmer-friendly here.

Cheers, Cliff

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