add/delete str/dt/cat dynamically from __dir__ (fix for #9627)

[mortada]

@jreback this PR makes it easier to add/delete items from __dir__. The .str/.dt/.cat are now only present in __dir__ when they are appropriate types.

However, the IPython tab completion does not seem to only source the list from __dir__, and therefore even if an item is removed from __dir__ it is still showing up in tab completion for me.

@shoyer I'd probably need some help/feedback with this. Here's a related ticket #9617

Thanks.

[jreback]

all of these accessors (cat,dt,str) are mutually exclusive, so should set in a single routine. IOW, maybe change delete all, then add back in an if-then

[shoyer]

I don't think we need to actually make a separate method _check_str_accessor(). You could simply do:

try:
    self.str
except AttributeError:
    # ...

[mortada]

I did that to avoid having to instantiate StringMethods(self) when it is not needed, but I agree it's probably premature optimization

[shoyer]

Some thoughts on the design here: we could add a class attribute _possible_accessors which corresponds to a set of all possibly accessors (e.g., Series._possible_acccessors = set(['cat', 'str', dt'])). Then we can have something like the following generic method defined on PandasObject:

def _dir_deletions(self):
    deletions = set()
    for accessor in self._possible_accessors:
        try:
            getattr(self, accessor)
        except AttributeError:
            deletions.add(accessor)
    return deletions

[mortada]

@shoyer I like this idea! I noticed that there's already a _accessors attribute under Series though

_accessors = frozenset(['dt', 'cat', 'str'])

but it's not obvious to me how this is being used.

[shoyer]

With regards to IPython auto-completion, this does seem trickier than I thought. Take a look at this example:

class A(object):
    something = 'asdf'

    def __dir__(self):
        return ['other']


class B(object):
    def __init__(self):
        self.something = 'asdf'

    def __dir__(self):
        return ['other']

a = A()
b = B()

Autocomplete on a still picks up something, even though we excluded it from __dir__ (on b, it's excluded). I'm guessing IPython uses dir(A) somehow.... might be worth asking over there, since I'm pretty puzzled at this point :).

[shoyer]

Yes, looks like _accessors is probably the appropriate attribute to use then :). You'll have to do some searching to figure out how it's currently used.

[mortada]

@shoyer updated to incorporate your suggestions, now using self._accessors
@jreback updated to make use of the fact that .str/.dt/.cat are mutually exclusive

[jreback]

lgtm

pls add a release note (use the pr number as the issue)

[shoyer]

you can equivalently use the built-in function dir here instead.

[shoyer]

LGTM, though you might test the built-in function dir directly instead of using __dir__

[mortada]

@shoyer that makes sense, it's updated

[shoyer]

OK, looks good to me! Please ping when it Travis is green.

Too bad this won't work for IPython auto-complete yet... but at least they're working on it.

[mortada]

travis is green now

yeah I hope the IPython auto-completion will work soon

[shoyer]

thanks!

[mortada]

great news - the issue has been closed on the IPython side, we should soon have the tab completion working