I am new to Python and am trying to write a function that will merge two dictionary objects in python. For instance

dict1 = {‘a’:[1], ‘b’:[2]}
dict2 = {‘b’:[3], ‘c’:[4]}

I need to produce a new merged dictionary

dict3 = {‘a’:[1], ‘b’:[2,3], ‘c’:[4]}

Function should also take a parameter “conflict” (set to True or False). When conflict is set to False, above is fine. When conflict is set to True, code will merge the dictionary like this instead:

dict3 = {‘a’:[1], ‘b_1’:[2],’b_2’:[3], ‘c’:[4]}

I am trying to append the 2 dictionaries, but not sure how to do it the right way.

for key in dict1.keys():
    if dict2.has_key(key):
        dict2[key].append(dict1[key])

If you want a merged copy that does not alter the original dicts and watches for name conflicts, you might want to try this solution:

>>> dict1 = {'a': [1], 'b': [2]}
>>> dict2 = {'b': [3], 'c': [4]}
>>> import copy
>>> import itertools
>>> def merge(a, b, conflict):
    new = copy.deepcopy(a)
    if conflict:
        for key, value in b.items():
            if key in new:
                counter = itertools.count(1)
                # Rename 1st key.
                while True:
                    name = '{}_{}'.format(key, next(counter))
                    if name not in new:
                        new[name] = new[key]
                        del new[key]
                        break
                # Create 2nd key.
                while True:
                    name = '{}_{}'.format(key, next(counter))
                    if name not in new:
                        new[name] = value
                        break
            else:
                new[key] = value
    else:
        for key, value in b.items():
            new.setdefault(key, []).extend(value)
    return new

>>> merge(dict1, dict2, False)
{'c': [4], 'b': [2, 3], 'a': [1]}
>>> merge(dict1, dict2, True)
{'b_2': [3], 'b_1': [2], 'c': [4], 'a': [1]}