1 List merge
Without for loop, you can directly use + or extend method
a=[1,2,3];b=[4,5,6]
a+b
Or a.extend(b)
[1,2,3,4,5,6]
If the list is large, + will be slower, and extend is better
2 Deduplication of list elements
Use set() to de-duplicate list elements
a=[1,2,3,4,2,3]
list(set(a))
3 List sorting
Use sort or the built-in function sorted to sort the list. There are two differences between them:
a sort () method is to operate on the original list, and the sorted () method will return a new list
b sort() is a method on the application list, and sorted() can sort all iterable objects
The default is ascending order, it can be changed to descending order
a.sort(reverse=True) #Descending order
4 Traverse the index and element pairs of the list
Use enumerate() function to output index and element value at the same time
a=["python","study"]
for i ,v in enumerate(a):
print (i, v)
5 Find the most frequently occurring element in the list
Use the max() function to quickly find the most frequently occurring element in a list
b=max(set(a),key=a.count)
6 Count the number of occurrences of all elements in the list
If you want to know the number of occurrences of all elements in the list, you can use the collections module. The collections module is a treasure module in python, which provides a lot of operation methods for sequences.
The counter method can perfectly solve this demand. Counter returns a dictionary
import random
import collections
lista=[]
for i in range(15):
lista.append(random.randint(1,10))
print(lista)
dicta=dict(collections.Counter(lista))
print(dicta)
#结果
[1, 6, 7, 1, 2, 1, 9, 7, 4, 5, 7, 10, 6, 5, 5]
{1: 3, 6: 2, 7: 3, 2: 1, 9: 1, 4: 1, 5: 3, 10: 1}
7 Combine the two lists into a dictionary
a=[1,2,3]
b=["one","two","three"]
dict(zip(a,b))
{1:"one",2:"two",3:"three"}
8 Remove a minimum and a maximum operation
a=[4,5,6,1]
minx,*mid,maxx=sorted(a)
print(mid)
[4,5]
Calculate the average sum(mid)/len(mid)
4.5
9 Ignore point model elements (implemented with underscore)
a=[4,5,6,1]
minx,_,*mid,maxx=sorted(a)
Ignore the second smallest element
print(mid) ====>5