如何在python中添加两个OrderedDict对象的值，并保持顺序？

Question

I would like to add two OrderedDict objects like these:

dict1 = OrderedDict([('Table', [10, 20, 30, 'wood']), ('Chair', [200, 300, 400, 'wood'])])
dict2 = OrderedDict([('Table', ['red', 55]), ('Chair', ['blue', 200])])

And create a new OrderedDict like this (the order is important):

dict3 = OrderedDict([('Table', [10, 20, 30, 'wood', 'red', 55]), ('Chair', [200, 300, 400, 'wood', 'blue', 200])])

If there are any keys in dict1 or dict2 that are not present in the other, those should be ignored, only matching keys should be used for the output. All values are lists.

Answer 1

Because you want to preserve the order of your OrderedDict objects, you need to loop over one and test each key against the other to produce the union of the two key sets:

dict3 = OrderedDict((k, dict1[k] + dict2[k]) for k in dict1 if k in dict2)

Looping over dict1 ensures that we output keys for the new dictionary in the same order, testing with k in dict2 ensures we only use keys that are present in both input mappings.

You can also update dict1 in-place with list.extend() :

for key, value in dict1.items():
    if key in dict2:
        value.extend(dict2[key])

Demo:

>>> from collections import OrderedDict
>>> dict1 = OrderedDict([('Table', [10, 20, 30, 'wood']), ('Chair', [200, 300, 400, 'wood'])])
>>> dict2 = OrderedDict([('Table', ['red', 55]), ('Chair', ['blue', 200])])
>>> OrderedDict((k, dict1[k] + dict2[k]) for k in dict1 if k in dict2)
OrderedDict([('Table', [10, 20, 30, 'wood', 'red', 55]), ('Chair', [200, 300, 400, 'wood', 'blue', 200])])

Answer 2

dict3 = {}
for i in dict1:
    if i in dict2:
        dict3[i]=[]
        for j in dict1[i]:
            dict3[i].append(j)
        for j in dict2[i]:
            dict3[i].append(j)