done this millions of times in other languages by python method for this is escaping me.
Basically reading some data from database. Includes data like ID, Fruits, Colors, Name
I need to create an object / dictionary key on Name. Name then holds lists / dictionaries of Fruits and Colors.
{"greenhouse1": {"fruits": {"apples", "oranges"}
{"colors": {"red","orange"}}
I'm iterating through the db by row and the Name key will appear more than once. When it does fruits or colors may already be populated and need to append.
namedict = {}
db_rows = execute_query(cursor, args.store_proc)
for row in db_rows:
db_name = row.id
db_fruit = row.fruit
db_color = row.color
if db_name in namedict:
namedict[db_name]["fruits"].append(db_fruit)
namedict[db_name]["color"].append(db_color)
else:
namedict[db_name]["fruits"] = [db_fruit]
namedict[db_name]["color"] = [db_color]
collections.defaultdict is your friend: If you access a new key of a defaultdict, it is automatically initialised with the provided function (list or set in this case). Because you want a dictionary (e.g. "greenhouse1") of dictionaries ("fruits", "colors") with lists as values (separate fruits and colors), we need a nested defaultdict. The following should work:
from collections import defaultdict
db = defaultdict(lambda: defaultdict(list)) # alternative: set instead of list
db['greenhouse1']['fruits'].append('apples') # use `add` for sets
db['greenhouse1']['fruits'].append('oranges')
db['greenhouse1']['colors'] = ["red", "orange"]
db['greenhouse2']['fruits'].append('banana')
print(db)
# defaultdict(<function __main__.<lambda>()>,
# {'greenhouse1': defaultdict(list,
# {'fruits': ['apples', 'oranges'],
# 'colors': ['red', 'orange']}),
# 'greenhouse2': defaultdict(list, {'fruits': ['banana']})})
A defaultdict works like a regular dict, so don't get confused with the strange looking output. E.g. to access the fruits of greenhouse1 you can simply write db['greenhouse1']['fruits'] and you get back a list (or set).