  # Python | Wise amount in a nested list column

NumPy | Python Methods and Functions

Examples :

`  Input:  [[1, 5, 3], [2, 7, 8], [4, 6, 9]]  Output:  [7, 18, 20]  Input:  [[20, 5], [2, 54], [45, 9], [72, 3]]  Output:  [139, 71] `

Method # 1: postal code, using list comprehension

We can find the sum of each column of a given nested list using the ` zip ` python function, enclosing it in a list.

 ` # Python3 program for nested list column wise sum `   ` def ` ` column_sum (lst): `   ` return ` ` [` ` sum ` ` (i) ` ` for ` ` i ` ` in ` ` zip ` ` (` ` * ` ` lst)] `   ` # Driver code ` ` lst ` ` = ` ` [[` ` 1 ` `, ` ` 5 ` `, ` ` 3 ` `], [` ` 2 ` `, ` ` 7 ` `, ` ` 8 ` `], [` ` 4 ` `, ` ` 6 ` `, 9 ]] `` print (column_sum (lst)) `

Output:

` [7, 18, 20] `

Method # 2: Using the map () method

Another way — use map () . We apply the sum function to each element in a column and find the sum of each column accordingly.

 ` # Python3 program for the column wise sum of the nested list `   ` def ` ` column_sum (lst): ` ` `  `  return list ( map ( sum , zip ( * lst))) ``   # Driver code `` lst = [[[ 1 , 5 , 3 ], [ 2 , 7 , 8 ], [ 4 , 6 , 9 ]] print (column_sum (lst)) `

Output:

` [7, 18, 20] `

Method # 3: Using numpy.sum ()

The numpy.sum () function returns the sum of the array elements along the specified axis.

 ` # Python3 program for the wise sum column of a nested list ` ` from ` ` numpy ` ` import ` ` array `   ` def ` ` column_sum (lst): ` ` arr ` ` = ` ` array (lst) ` ` return ` ` sum ` ` (arr, ` ` 0 ` `). tolist () `   ` # Driver code ` ` lst ` ` = ` ` [[` ` 1 ` `, ` ` 5 ` `, ` ` 3 ` `], [` ` 2 ` `, ` ` 7 ` `, ` ` 8 ` `], [` ` 4 ` `, ` ` 6 ` `, ` ` 9 ` `]] ` ` print ` ` (column_sum (lst)) `

Output:

` [7, 18, 20] `