CODEWITHSUNDEEP
pythondictionaryenthoughttraitstraitsui
Adam Hughes
Adam Hughes

Reputation: 16309

Enthought Traits.HasTraits class as a nested dictionary?

Imagine I have the following Traits objects:

from traits.api import Int, HasTraits, Instance

class Foo(HasTraits):
    a = Int(2)
    b = Int(5)

class Bar(HasTraits):
    c = Int(7)
    foo = Instance(Foo,())

Bar will let me access attribute a on Foo via:

bar = Bar()
bar.foo.a
>>> 2

Is there a standard way to return bar as a nested dictionary of the form:

print bar_as_dict 
>>> {'c':7, 'foo':{'a':2, 'b':5}}

I'm essentially trying to extract all subtraits on an object that are a particular type. Our use case is we have deeply-nested HasTrait objects that have plot traits, and we are trying to dynamically find all the plots on a particular object. We have a function that can return the plots from a nested dictionary, but we need to pass HasTrait objects in, so formatting them into nested dictionaries would be great. If there is another way to dynamically inspect the stack of a HasTraits object and return all traits of a certain type, that would work too.

Here's a link to the HasTraits API... couldn't figure this out directly from that.

Solution Attempt

I've tried using the .traits() method, but it returns these CTrait objects.

print bar.traits()
>>>{'trait_added': <traits.traits.CTrait object at 0x8b7439c>,
 'c': <traits.traits.CTrait object at 0x8b29e9c>, 
'foo': <traits.traits.CTrait object at 0x8b29e44>, 
'trait_modified': <traits.traits.CTrait object at 0x8b74344>}

Which don't evaluate as I'd expect:

isinstance(bar.traits()['c'], int)
>>> False

But after Pieter's suggestion, this works:

print bar.traits()['c'].is_trait_type(Int)
>>> True

Now the question is how to do this recursively.

Upvotes: 3

Views: 347

Answers (1)

Adam Hughes
Adam Hughes

Reputation: 16309

I figured it out after following a similar question on recursion of a nested dictionary without Trait values

def flatten_traitobject(traitobject, *types):
    node_map = {}
    node_path = [] 
    def nodeRecursiveMap(traitobject, node_path): 
        for key in traitobject.editable_traits():
            val = traitobject.get(key)[key]
            for type in types:
                if isinstance(val, types[0]):
                    node_map['.'.join(node_path + [key])] = val 
            try:
                nodeRecursiveMap(val, node_path + [key])
            except (AttributeError, TypeError):
                pass
    nodeRecursiveMap(traitobject, node_path)
    return node_map

Testing it out, I can choose to retain only integers and/or only objects of type Foo

bar=Bar()
print 'RETAINING ONLY INTEGER TYPES'
print flatten_traitobject(bar, int)
print '\nRETAINTING ONLY FOO OBJECT TYPES'
print flatten_traitobject(bar, Foo)

>>> RETAINING ONLY INTEGER TYPES
>>> {'c': 7, 'foo.b': 5, 'foo.a': 2}

>>> RETAINTING ONLY FOO OBJECT TYPES
>>> {'foo': <__main__.Foo object at 0x8f9308c>}

Foo represents the special plotting traits I'm after, so I can effectively return them now.

Upvotes: 1

Related Questions