provide example of list of dictionaries and filtering by intermediate key

[binki]

Say I have this:

d = {'x': [{'a': 5, 'b': 2}, {'a': 6, 'b': 4}]}

and I want to list all the values of a. I cannot get from the README that I would use:

dpath.util.values(d, '/x/*/a')

Also, how can I look up the value of 'b' for when 'a' is 6, for example? Is there a place to look for documentation (that could be linked from the README?) Am I not looking for docs in the right place just because I’m unfamiliar with python? ;-)

Thanks for any help or doc updates!

[xhh2a]

dpath:

>>> import dpath.util
>>> d = {'x': [{'a': 5, 'b': 2}, {'a': 6, 'b': 4}]}
>>> dpath.util.values(d, 'x')
[[{'a': 5, 'b': 2}, {'a': 6, 'b': 4}]]
>>> dpath.util.values(d, 'x/*')
[{'a': 5, 'b': 2}, {'a': 6, 'b': 4}]
>>> dpath.util.values(d, 'x/*/**/a')
[5, 6]

funcy:

>>> from funcy import get_in
>>> get_in(d, ["x"])
[{'a': 5, 'b': 2}, {'a': 6, 'b': 4}]
>>> from funcy import pluck
>>> pluck("a", get_in(d, ["x"]))
[5, 6]

[akesterson]

@xhh2a answered your first question nicely, so I'll focus on the second.

Also, how can I look up the value of 'b' for when 'a' is 6, for example?

This is not explicitly documented (not every use case is in the documentation). This is currently a 2 step process (though a more elegant solution is currently being discussed in #40 ).

>>> for (path, value) in dpath.util.search(d, '/x/*/a', afilter=(lambda x: x == 6), yielded=True):
...     parentpath = path.split('/')[:-1]
...     print dpath.util.search(d, '/'.join([parentpath, 'b']))
... 
{'x': [{'b': 4}]}

I'm going to make a master ticket for documentation updates and link this from there; closing for now.

[abarnert]

I think @binki was asking why this works:

>>> dpath.util.values(d, '/x/*/a')
[5, 6]

… rather than complaining that it doesn't work and asking what to do instead, which is what @xhh2a answered.

But it does work, and if you just had a single example showing a * glob pattern, it would be obvious why.

Right now, there is such an example, but it's wrong: the '/a/b/d/\*' won't match anything (see #80 for why it wouldn't even match a literal '*' key), and what you really want is /a/b/d/*. Although even then it's kind of pointless, because you'll get the same results from a/b/d. A better example might be showing multiple searches: a/*/d/0, a/b/*/0, a/**/0.