Python--Counter class

Python--Counter class

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Reference

Official documents

Class collections. Counter ([iterable-or-mapping])

Counter is integrated into the Dict class, so you can also use the dictionary method, which returns a collection of Counter objects with element key and number of elements as value

>>> from collections import Counter>>> s = "hello pinsily">>> d = Counter(s)>>> dCounter({‘l‘: 3, ‘i‘: 2, ‘h‘: 1, ‘e‘: 1, ‘o‘: 1, ‘ ‘: 1, ‘p‘: 1, ‘n‘: 1, ‘s‘: 1, ‘y‘: 1})

Elements ()

Returns an iterator

>>> d.elements()<itertools.chain object at 0x0000019AC812BBA8># 可以进行打印和排序>>> for i in d.elements():...     print(i)...

Most_common (N)

Returns the highest number of first n elements

>>> d.most_common(3)[(‘l‘, 3), (‘i‘, 2), (‘h‘, 1)]

Subtract ([iterable-or-mapping])

Equivalent to subtraction, Counter that call this method will be overwritten.

>>> c = Counter(a=4, b=2, c=0, d=-2)>>> d = Counter(a=1, b=2, c=3, d=4)>>> c.subtract(d)>>> cCounter({‘a‘: 3, ‘b‘: 0, ‘c‘: -3, ‘d‘: -6})>>> dCounter({‘d‘: 4, ‘c‘: 3, ‘b‘: 2, ‘a‘: 1})

Summarize

When you need to count a large amount of data in a list, you can use Counter directly instead of creating a new dictionary to count

Python--Counter class