Question

How do I look up the ‘id’ associated with the a person’s ‘name’ when the 2 are in a dictionary?

user = 'PersonA'
id = ? #How do I retrieve the 'id' from the user_stream json variable?

json, stored in a variable named “user_stream”

[
  {
    'name': 'PersonA',
    'id': '135963'
  },
  {
    'name': 'PersonB',
    'id': '152265'
  },
]

Answer 1

You’ll have to decode the JSON structure and loop through all the dictionaries until you find a match:

for person in json.loads(user_stream):
    if person['name'] == user:
        id = person['id']
        break
else:
    # The else branch is only ever reached if no match was found
    raise ValueError('No such person')

If you need to make multiple lookups, you probably want to transform this structure to a dict to ease lookups:

name_to_id = {p['name']: p['id'] for p in json.loads(user_stream)}

then look up the id directly:

id = name_to_id.get(name)  # if name is not found, id will be None

The above example assumes that names are unique, if they are not, use:

from collections import defaultdict

name_to_id = defaultdict(list)
for person in json.loads(user_stream):
    name_to_id[person['name']).append(person['id'])

# lookup
ids = name_to_id.get(name, [])  # list of ids, defaults to empty

This is as always a trade-off, you trade memory for speed.