python-dictionary-notes.md

Python Dictionary Notes

Creating a dictionary whose default is a zero

This can be useful for looping through a collection and building up counts. The defaultdict is a dictionary-like data structure.

from collections import defaultdict

chars_hash = defaultdict(int) # default value for undefined key is zero int
for char in 'apple':
    chars_hash[char] += 1

print(chars_hash)
#=> defaultdict(<class 'int'>, {'a': 1, 'p': 2, 'l': 1, 'e': 1})