If key already exists in a dict, how to add multiple values to it (Python)

Question

I'm looping through steps in a dictionary and pulling out a contact phone number and an id for each step, and put these as key/value pairs into a new dict: contacts

contacts = {}

for execution_step in execution_steps["steps"]:
    main_execution_context = get_execution_context(execution_step["url"])
    contact_phone = main_execution_context["contact"]
    id = main_execution_context["id"]
    contacts[contact_phone] = id

Where there are duplicates of contact_phone i.e. the key already exists, is it possible to append the value pair (id) onto the existing value, thus creating a list of id's associated with the same phone number?

Check out [this](https://stackoverflow.com/questions/20585920/how-to-add-multiple-values-to-a-dictionary-key-in-python) — 0x263A, Sep 09 '21 at 14:54
Check [this](https://docs.python.org/3/library/collections.html#defaultdict-examples) out... `defaultdict(list)` — Suyog Shimpi, Sep 09 '21 at 15:48

not_speshal · Accepted Answer · 2021-09-09T15:31:07.940

0

Save every value as a list. If the key exists, append to the list.

contacts = {}

for execution_step in execution_steps["steps"]:
    main_execution_context = get_execution_context(execution_step["url"])
    contact_phone = main_execution_context["contact"]
    if contact_phone not in contacts:
        contacts[contact_phone] = list()
    contacts[contact_phone].append(main_execution_context["id"])

Edit:

To add new keys:

contacts["example_number"] = list()
contacts['example_number'].append(main_execution_context["id"])

Or:

contacts["example_number"] = [main_execution_context["id"]]

edited Sep 09 '21 at 15:31

answered Sep 09 '21 at 14:54

not_speshal

22,093
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Thank you! How am I able to add new keys into the contacts dict? At the moment when I try to add a new key I am getting a KeyError on 'example_number' when running the following: contacts['example_number'].append(main_execution_context["id"]) – price88 Sep 09 '21 at 15:22

score 0 · Answer 2 · answered Sep 09 '21 at 14:55

0

You can use the defaultdict. Only key codes are shown:

from collections import defaultdict
contacts = defaultdict(list)
contacts[contact_phone].append(id)

answered Sep 09 '21 at 14:55

chenzhongpu

6,193
8
41
79

If key already exists in a dict, how to add multiple values to it (Python)

2 Answers2

Edit: