Question

When I want to append a newvalue into Dict under Key, I find myself have to write:

# Dict={}
# Key = ....
# newvalue = ....

if not Key in Dict:
    Dict[Key] = [ newvalue ]
else:
    Dict[Key].append(newvalue)

It costs four lines of code. Is there a more concise way with python standard library? e.g

Dict.appendkeyvalue(Key, newvalue)

Answer 1

You can use a defaultdict:

from collections import defaultdict

d = defaultdict(list)

d['something'].append(3)
print d['something']
# > [3]