Python learning-the frequency with which elements appear in a statistical sequence (number of times)

For example, there is a list

L=[1,1,-1,2,3,22,34,32,2,-3,34,22,-5]

How many times each element appears in the statistics list

Way One:

Turn the list into a dictionary dict, the dictionary key corresponds to each element in the list, and value represents the number of occurrences of each element.

D=dict.fromkeys (l,0) #两个参数, the first parameter is the corresponding list, and the second parameter sets the default value=0 for Dict.

Then, traversing each element in the list, the element is encountered in the Dict, and value is added 1.

For X in L:

D[l]+=1

Print (d)

Way two:

Take advantage of the counter subclass of the collection.

From collections Import Counter

C=counter (L) #直接把列表l传入Counter, returns a dict, the key in this dict corresponds to each element in the set, and value represents the number of occurrences of this element in the collection

Print (C.most_common (3)) #Counter类的most_common () method returns a value from a large to a small list, returning n most common elements The list and its number.

Python learning-the frequency with which elements appear in a statistical sequence (number of times)