Counter and defaultdict
Replace the sentence with your own and see which word is most common.
The standard library module collections adds specialised containers: Counter for counting, defaultdict for grouping, deque for fast work at both ends, namedtuple for records, OrderedDict for order-aware dictionaries and ChainMap for layered lookups.
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Practice questions
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Use Counter to find the most common letter in "mississippi" and print it with its count.
Group ["apple", "avocado", "banana", "blueberry", "cherry"] by first letter using defaultdict(list) and print it as a normal dict.
Keep only the last 3 numbers of [1, 2, 3, 4, 5, 6] using a deque with maxlen, and print them as a list.
Explain it without notes
What problem do Counter and defaultdict solve compared with a plain dict?
Why choose deque instead of a list for a queue?
When would you use ChainMap?
How does a namedtuple differ from a regular tuple and from a dictionary?
How would you build a small LRU (least recently used) cache with the standard library?
Expected output
counts: Counter({'to': 3, 'be': 3, 'or': 1, 'not': 1, 'that': 1, 'is': 1, 'the': 1, 'question': 1})
top 2: [('to', 3), ('be', 3)]
'to' appears: 3 | 'zebra' appears: 0
after update: 2
letters: Counter({'a': 3, 'n': 2, 'b': 1})
by length: {3: ['pen', 'bag', 'ink'], 4: ['book', 'desk']}
tally: {'m': 1, 'i': 4, 's': 4, 'p': 2}