Merge Two Dictionaries And Persist The Values Of First Dictionaries

I have two dictionaries: first = {'phone': { 'home': '(234) 442-4424' }, 'address':'xyz' } second = {'phone': {

Solution 1:

Do second.update(first). Any keys in both will have their value set to the value in first and any keys that are in first but not second will be added to second.

Solution 2:

Update() will work, simply copy the second dict and apply the first one. So the value of the first will replace the second and not the reverse way.

first = {"phone": {"home": "(234) 442-4424"},"address":"xyz"}
second = {"phone": {"home": "(234) 442-5555","home1": "(234) 442-4424"},"address":{}}

# recursive deep update you can find here: http://stackoverflow.com/a/3233356/956660import collections

defupdate(d, u):
    for k, v in u.iteritems():
        ifisinstance(v, collections.Mapping):
            r = update(d.get(k, {}), v)
            d[k] = r
        else:
            d[k] = u[k]
    return d

third = second.copy()
update(third, first)

print(third)

{'phone': {'home': '(234) 442-4424', 'home1': '(234) 442-4424'}, 'address': 'xyz'}

Solution 3:

If you want to just add the missing key/value pairs into the first dictionary, you can just add them to the first instead of creating a new dictionary.

first = {}
second = {}

for key in second.keys():
  if key not in first:
    first[key] = second[key]

---

Edit: your comment "it wont work with multilevel dictionary"

Actually, it will..technically speaking.

first = {"Person1" : {"Age": "26", "Name": "Person1", "Phone number": "XXXXXX"}}
second = {"Person1": {"Interests": "fishing"}, "Person2": {"Age": "26", "Name": "Person2", "Phone number": "XXXXXX"}}

In this case, the firstdict will get the Person2object, but will not change the Person1 object, as it is already there!

Solution 4:

Assuming your dictionnaries have following structure:

• each element is a dictionnary
• values are either plain strings or dictionnaries

Assuming that the requirement is:

• if a key exist only in one of the 2 elements to merge, keep its value
• if a key exists in both elements:
  • if the value in first element is a plain string, keep its value
  • if the value in first element is a dict and the value in second is a string, keep value from first
  • if the values in both elements are dict merge them with priority to first

A possible code is then:

for k, v in first.iteritems():
    if isinstance(v, str):
        final[k] = v
    elif k infinal:
        if isinstance(final[k], dict):
            final[k].update(first[k])
        else:
            final[k] =first[k]
    else:
        final[k] =first[k]