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Python | Uneven Sized Matrix Column product

  • Last Updated : 30 Dec, 2020

The usual list of list, unlike conventional C type Matrix, can allow the nested list of lists with variable lengths, and when we require the product of its columns, the uneven length of rows may lead to some elements in that elements to be absent and if not handled correctly, may throw exception. Let’s discuss certain ways in which this problem can be performed in error free manner.

Method #1 : Using loop + filter() + map() + list comprehension
The combination of above three function combined with list comprehension can help us perform this particular task, the external prod function helps to perform the multiplication, filter allows us to check for the present elements and all rows are combined using the map function. Works only with python 2.




# Python code to demonstrate 
# Uneven Sized Matrix Column product
# using loop + filter() + map() + list comprehension
  
# getting Product 
def prod(val) : 
    res = 1 
    for ele in val: 
        res *= ele 
    return res 
  
# initializing list of lists
test_list = [[1, 5, 3], [4], [9, 8]]
  
# printing original list 
print ("The original list is : " + str(test_list))
  
# using loop + filter() + map() + list comprehension
# Uneven Sized Matrix Column product
res = [prod(filter(None, j)) for j in map(None, *test_list)]
  
# printing result
print ("The product of columns is : " + str(res))
Output :
The original list is : [[1, 5, 3], [4], [9, 8]]
The product of columns is : [36, 40, 3]

 

Method #2 : Using list comprehension + loop + zip_longest()
If one desires not to play with the None values, one can opt for this method to resolve this particular problem. The zip_longest function helps to fill the not present column with 1 so that it does not has to handle the void of elements not present.






# Python3 code to demonstrate 
# Uneven Sized Matrix Column product
# using list comprehension + loop + zip_longest()
import itertools
  
# getting Product 
def prod(val) : 
    res = 1 
    for ele in val: 
        res *= ele 
    return res 
  
# initializing list of lists
test_list = [[1, 5, 3], [4], [9, 8]]
  
# printing original list 
print ("The original list is : " + str(test_list))
  
# using list comprehension + loop + zip_longest()
# Uneven Sized Matrix Column product
res = [prod(i) for i in itertools.zip_longest(*test_list, fillvalue = 1)]
  
# printing result
print ("The product of columns is : " + str(res))
Output :
The original list is : [[1, 5, 3], [4], [9, 8]]
The product of columns is : [36, 40, 3]

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