How to delete values in a dict based on the presence of child values-CodePudding

I have a dict that looks like this:

OrderedDict([('arguments', {'index': 1, 'parent': None}), ('controls', {'index': 2, 'parent': None}), ('examples', {'index': 3, 'parent': None}), ('journal', {'index': 4, 'parent': None}), ('journal/config', {'index': 5, 'parent': 'journal'}), ('journal/journaltest', {'index': 6, 'parent': 'journal'}), ('procs', {'index': 7, 'parent': None}), ('processor', {'index': 8, 'parent': None}), ('prediction', {'index': 9, 'parent': None}), ('reports', {'index': 10, 'parent': None}), ('tooki', {'index': 11, 'parent': None}), ('tooki/help', {'index': 12, 'parent': 'tooki'}), ('tooki/lime', {'index': 13, 'parent': 'tooki'}), ('tooki/medium', {'index': 14, 'parent': 'tooki'}), ('tooki/share', {'index': 15, 'parent': 'tooki'}), ('tooki/trigger', {'index': 16, 'parent': 'tooki'})])

How can I iterate over the elements of this dict, and exclude any element that has "'parent' : None" and no child element (meaning, no other element in this dict has this one as a parent).

Expected output:

OrderedDict([('journal', {'index': 4, 'parent': None}), ('journal/config', {'index': 5, 'parent': 'journal'}), ('journal/journaltest', {'index': 6, 'parent': 'journal'}), ('tooki', {'index': 11, 'parent': None}), ('tooki/help', {'index': 12, 'parent': 'tooki'}), ('tooki/lime', {'index': 13, 'parent': 'tooki'}), ('tooki/medium', {'index': 14, 'parent': 'tooki'}), ('tooki/share', {'index': 15, 'parent': 'tooki'}), ('tooki/trigger', {'index': 16, 'parent': 'tooki'})])

CodePudding user response：

ins = OrderedDict(...)

parents = set(elem['parent'] for elem in ins.values() if elem['parent'] is not None)

d = OrderedDict()
for key, value in ins.items():
    if value['parent'] is not None:
        d[key] = value
    elif any(ins.get(k) is not None for k in parents):
        d[key] = value

Using a set of parent keys remove lot of complexity. In your case, there are lot of elements, but only two keys will be checked.

CodePudding user response：

A really dumb way of doing this:

x = OrderedDict(blah blah blah)

keys_to_exclude = []
for key1, val1 in x.items():
    if val1['parent'] is None:
        remove = True
        for key2, val2 in x.items():
            if val2['parent'] == key1:
                remove = False  
        if remove:
            keys_to_exclude.append(key1)

for key in keys_to_exclude:
    x.pop(key, None)

This code obviously had O(n^2) complexity. A smarter way of doing this would be adding a 'child' key for each element beforehand and the complexity would be O(n).

CodePudding user response：

Here is something that working for me. The order of the final output is not the same, but I was able to meet the requirement of excluding the key value pairs according to the conditions you had mentioned.

a = OrderedDict([('arguments', {'index': 1, 'parent': None}),
                 ('controls', {'index': 2, 'parent': None}),
                 ('examples', {'index': 3, 'parent': None}),
                 ('journal', {'index': 4, 'parent': None}),
                 ('journal/config', {'index': 5, 'parent': 'journal'}),
                 ('journal/journaltest', {'index': 6, 'parent': 'journal'}),
                 ('procs', {'index': 7, 'parent': None}),
                 ('processor', {'index': 8, 'parent': None}),
                 ('prediction', {'index': 9, 'parent': None}),
                 ('reports', {'index': 10, 'parent': None}),
                 ('tooki', {'index': 11, 'parent': None}),
                 ('tooki/help', {'index': 12, 'parent': 'tooki'}),
                 ('tooki/lime', {'index': 13, 'parent': 'tooki'}),
                 ('tooki/medium', {'index': 14, 'parent': 'tooki'}),
                 ('tooki/share', {'index': 15, 'parent': 'tooki'}),
                 ('tooki/trigger', {'index': 16, 'parent': 'tooki'})])
od = OrderedDict()
for each in a:
    if (parent := a[each].get('parent', None)):
        od[parent] = a[parent]

for each in a:
    if (element := a[each].get('parent', None)):
        od[each] = a[each]

print(od)

I did not comprehension for simplicity of understanding the code. The first loop saves the parents to a new OrdereDict. The second saves the children. Do let me know if your requirements are not met.