How to add a new pair of key(str) and value(list) and append an int in the value list

santosbogo 0
Viewed 36

I have the following code. I can't find the way of creating a new key and append a number to the value list.

from typing import Dict, List, Set

diccionary: Dict[str, List[int]]
diccionary = {}

diccionary["key"].append(2)
diccionary["key2"].append(4)
diccionary["key2"].append(1)

print(diccionary)

When I run this code I get:

Traceback (most recent call last):
  File "diccionario.py", line 5, in <module>
    diccionario["key"].append(2)
KeyError: 'key'
data-structures python-3.x python
1 Answers

Use setdefault:

diccionary = {}
diccionary.setdefault("key", []).append(2)
diccionary.setdefault("key2", []).append(4)
diccionary.setdefault("key2", []).append(1)

print(diccionary)

Or, use a defaultdict:

from collections import defaultdict

diccionary = defaultdict(list)

diccionary["key"].append(2)
diccionary["key2"].append(4)
diccionary["key2"].append(1)

print(dict(diccionary))

Output:

{'key': [2], 'key2': [4, 1]}
mozway0
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