Counting Tips
Learn the appropriate use of counter in your program.
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Count with defaultdict
When we count the number of occurrences of a particular item in an iterable (say, a specific character in a string), we use an integer number as a counter. When the iterable consists of heterogeneous items and we know the number of their types ahead of time, we can use a list of counters, especially if the item types map nicely to list indexes. If the number of types is large or unknown, a dictionary is the best counting tool. We iterate through the iterable and check if we’ve seen the next item before. If so, we increment its counter in the ...