Python|将子列表中的每个元素乘以其索引

给定一个列表列表，任务是将子列表中的每个元素乘以其索引并返回一个求和列表。

下面给出一些解决问题的方法。

方法#1：使用朴素方法

# Python3 code to demonstrate
# to multiply numbers with position
# and add them to return num
  
import numpy as np
  
# initialising list
ini_list = [[3, 4, 7], [ 6, 7, 8], [ 10, 7, 5], [ 11, 12, 13]]
  
# printing initial_list
print ("initial_list ", ini_list)
  
res = []
# Using Naive Method
for sub_list in ini_list:
    sublistsum = 0
  
    for i, value in enumerate(sub_list):
        sublistsum = sublistsum + i * value
  
    res.append(sublistsum)
  
# printing result
print ("result", res)

输出：

initial_list  [[3, 4, 7], [6, 7, 8], [10, 7, 5], [11, 12, 13]]
result [18, 23, 17, 38]

方法#2：使用列表推导

# Python3 code to demonstrate
# to multiply numbers with position
# and add them to return num
  
  
# initialising list
ini_list = [[3, 4, 7], [ 6, 7, 8], [ 10, 7, 5], [ 11, 12, 13]]
  
# printing initial_list
print ("initial_list ", ini_list)
  
# Using list comprehension
res = [sum(i * j for i, j in enumerate(sublist)) 
                         for sublist in ini_list]
  
# printing result
print ("result", res)
             

输出：

initial_list  [[3, 4, 7], [6, 7, 8], [10, 7, 5], [11, 12, 13]]
result [18, 23, 17, 38]

方法 #3：使用 numpy

# Python3 code to demonstrate
# to multiply numbers with position
# and add them to return num
  
import numpy as np
  
# initialising list
ini_list = [[3, 4, 7], [ 6, 7, 8], [ 10, 7, 5], [ 11, 12, 13]]
  
# printing initial_list
print ("initial_list ", ini_list)
  
# Using numpy
res = [np.arange(len(sublist)).dot(sublist) for sublist in ini_list]
  
# printing result
print ("result", res)
              
             

输出：

initial_list  [[3, 4, 7], [6, 7, 8], [10, 7, 5], [11, 12, 13]]
result [18, 23, 17, 38]