Add some documentation on gotchas related to pytz updates #7620

[rockg]

closes #7620

[jreback]

can u make this pytz/dateutil (or just say tz library)

as this is a function. of the time zone definitions and not the tz library itself

[rockg]

Done.

Also, the ipython slowness was actually due to how completion is implemented in PyDev. It does dir(object) and then iterates through the attributes calling getattr in order to call inspect.getdoc. With a large DatetimeIndex, getattr for properties evaluates the property and some of those take 15 seconds. Trying to work out a solution to that on the PyDev side.

[immerrr]

@rockg, if that's of any help, I've recently pushed a fix into ipython introspection utilities to avoid evaluating properties in the last step of the lookup when doing question-mark queries, e.g. obj.this_is_evaluated.this_is_not? It ended up pretty simple, maybe you can borrow some inspiration from there.

[jreback]

@jorisvandenbossche ?

[jorisvandenbossche]

looks ok. Does this close #7620 ?

[rockg]

@immerrr Thank you for the reference. I was doing something similar. I simply did:

try:
   obj = getattr(type(parent_obj), attr)
except AttributeError:
   obj = getattr(parent_obj, attr)
except:
   continue