Python · Iterators, modules and the standard library

collections.defaultdict

A dictionary that creates a default value for missing keys.

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Syntax

defaultdict(list)

Example

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from collections import defaultdict
by_first = defaultdict(list)
for tag in ["css", "csharp", "html"]:
    by_first[tag[0]].append(tag)
print(dict(by_first))

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collections.defaultdict

Example

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