I have a nested dictionary, i.e.
a={'k1':{'k2':1}}
I would like to write a function
def f(dictionary,key_list):
pass
such that f(a,['k1','k2']) would be equivalent to del(a['k1']['k2'])
I tried to use
from functools import reduce
import operator
def f(dictionary,key_list):
reduce(operator.delitem,key_list,dictionary)
However
f(a,['k1','k2'])
returns
TypeError: 'NoneType' object does not support item deletion
You only want to delete from the innermost dictionary, not from the outer dictionaries. So for the path to get to the innermost dictionary you need to use getitem, not delitem. Only the last key should be used for deletion:
def f(dictionary, key_list):
*path, key = key_list
del reduce(operator.getitem, path, dictionary)[key]
Demo (with one more level to be clearer):
from functools import reduce
import operator
def f(dictionary, key_list):
*path, key = key_list
del reduce(operator.getitem, path, dictionary)[key]
a = {'k1': {'k2': {'k3': 1}}}
f(a, ['k1', 'k2', 'k3'])
print(a)
That prints {'k1': {'k2': {}}}, same as after del a['k1']['k2']['k3']:
a = {'k1': {'k2': {'k3': 1}}}
del a['k1']['k2']['k3']
print(a)
I would reduce on dict.get over all but the last key to find the inner-most dictionary, then invoke del on that dict using the final key.
def f(dictionary,key_list):
dictionary = reduce(dict.get, key_list[0:-1], dictionary)
del dictionary[key_list[-1]]
a={'k1':{'k2':1}}
print(a)
f(a,['k1','k2'])
print(a)
Result:
$ python x.py
{'k1': {'k2': 1}}
{'k1': {}}
operator.delitemreturnsNone.