CODEWITHSUNDEEP
pythonnumpycollectionsdefaultdict
zinjaai
zinjaai

Reputation: 2385

Creating a defaultdict with empty numpy array

I'm wondering if there's a more clever way to create a default dict from collections. The dict should have an empty numpy ndarray as default value.

My best result is so far:

import collections
d = collections.defaultdict(lambda: numpy.ndarray(0))

However, i'm wondering if there's a possibility to skip the lambda term and create the dict in a more direct way. Like: 

d = collections.defaultdict(numpy.ndarray(0))  # <- Nice and short - but not callable

Upvotes: 14

Views: 15729

Answers (2)

smttsp
smttsp

Reputation: 4191

Another way is the following if you know the array size beforehand:

new_dict = defaultdict(lambda: numpy.zeros(array_size))

Upvotes: 4

Martijn Pieters
Martijn Pieters

Reputation: 1123250

You can use functools.partial() instead of a lambda:

from collections import defaultdict
from functools import partial

defaultdict(partial(numpy.ndarray, 0))

You always need a callable for defaultdict(), and numpy.ndarray() always needs at least one argument, so you cannot just pass in numpy.ndarray here.

Upvotes: 24

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