[issue28612] str.translate needs a mapping example

Cheryl Sabella added the comment: IDLE just added similar functionality to pyparse (issue 32940) using: class ParseMap(dict): def __missing__(self, key): return 120 # ord('x') # Map all ascii to 120 to avoid __missing__ call, then replace some.

[issue28612] str.translate needs a mapping example

Christopher Barker added the comment: This all came out of a thread on python-ideas, starting here: https://mail.python.org/pipermail/python-ideas/2016-October/043284.html the thread kind of petered out, but it seems there was a kinda-sorta consensus that we didn't need any new string methods,

[issue28612] str.translate needs a mapping example

Gaurav Tatke added the comment: Should a user be suggested to use str.translate() for the use case where user only wants to keep certain characters and strip off everything else? -- ___ Python tracker

[issue28612] str.translate needs a mapping example

Gaurav Tatke added the comment: Hi, Pardon my ignorance, I am new to this but have below queries/thoughts - 1. Why would we say that adding new keys during lookup phase is an unpleasant side-effect? From what I understood by docs, one of the main reasons to use defaultdicts is to be able to

[issue28612] str.translate needs a mapping example

Serhiy Storchaka added the comment: If the side effect of defaultdict is unpleasant, the correct way is combining the translation mapping with the custom mapping by ChainMap. But this example is too complex for the documentation of str.translate(). On other side, it is trivial for more

[issue28612] str.translate needs a mapping example

Raymond Hettinger added the comment: I like the idea of adding a mapping example but don't want to encourage use of defaultdict in contexts like this one. A defaultdict usefully specifies a default but has the unpleasant side-effect of altering the dictionary (adding new keys) during the

[issue28612] str.translate needs a mapping example

Gaurav Tatke added the comment: Hi, I am new to Python and want to contribute. I am attaching a patch having required example of using defaultdict with translate. Please let me know if anything needs to be changed. I have tested the example and also the html doc in my local. Regards, Gaurav

[issue28612] str.translate needs a mapping example

Chris Barker added the comment: Agreed: the custom dict type would be nice for a recipe or blog post or... but not for the docs. I'll note that the other trick to this recipe is that you need to know to use lambda to make a "None factory" for defaultdict -- though maybe that's a ToDo for

[issue28612] str.translate needs a mapping example

Jim Jewett added the comment: https://mail.python.org/pipermail/python-ideas/2016-November/043539.html by Chris Barker points out that a custom object (which doesn't ever store the missing "keys") may be better still... though I'm not sure it is better enough to complicate the docs.

[issue28612] str.translate needs a mapping example

New submission from Jim Jewett: One commonly needed string transformation is stripping out certain characters (or only keeping certain characters). This is common enough that it might be worth a dedicated method, except, that, as Stephen J. Turnbull wrote in