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Python program to find product of given number of consecutive elements
  • Last Updated : 02 Feb, 2021

Given a List, the task is to write a python program that can construct a list with products of consecutive elements for a given number of elements.

Input : test_list = [5, 6, 2, 1, 7, 5, 3], K = 3

Output : [60, 12, 14, 35, 105]

Explanation : 5 * 6 * 2 = 60, 6 * 2 * 1 = 12.. And so on.

Input : test_list = [5, 6, 2, 1, 7, 5, 3], K = 4



Output : [60, 84, 70, 105]

Explanation : 5 * 6 * 2 * 1 = 60, 6 * 2 * 1 * 7 = 84.. And so on.

Method 1 : Using list slicing and loop

In this, we perform task of getting K slice using list slicing and task of getting product is done by an external function call.

Example:

Python3




# getting product
def prod(sub):
    res = 1
    for ele in sub:
        res = ele * res
    return res
  
  
# initializing lists
test_list = [5, 6, 2, 1, 7, 5, 3]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K
K = 3
  
res = []
for idx in range(len(test_list) - K + 1):
  
    # getting product using external function
    res.append(prod(test_list[idx: idx + K]))
  
# printing result
print("Computed Products : " + str(res))

Output:

The original list is : [5, 6, 2, 1, 7, 5, 3]

Computed Products : [60, 12, 14, 35, 105]



Method 2 : Using generator, slicing, reduce() and mul operator

In this, generator is used to compute and return intermediate result. Task of getting sliced multiplication is done using inbuilt function reduce(), and mul operator.

Example:

Python3




from functools import reduce
from operator import mul
  
# generator function
  
  
def sliced_prod(sub, K):
    for idx in range(len(sub) - K + 1):
  
        # slicing and returning intermediate product
        sliced = sub[idx: idx + K]
        yield reduce(mul, sliced)
  
# generator function
  
  
# initializing lists
test_list = [5, 6, 2, 1, 7, 5, 3]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K
K = 3
  
# calling fnc.
res = list(sliced_prod(test_list, K))
  
# printing result
print("Computed Products : " + str(res))

Output:

The original list is : [5, 6, 2, 1, 7, 5, 3]

Computed Products : [60, 12, 14, 35, 105]

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