numpy.sum() in Python

numpy.sum(arr, axis, dtype, out) : This function returns the sum of array elements over the specified axis.

Parameters :
arr : input array. 
axis : axis along which we want to calculate the sum value. Otherwise, it will consider arr to be flattened(works on all the axis). axis = 0 means along the column and axis = 1 means working along the row. 
out : Different array in which we want to place the result. The array must have same dimensions as expected output. Default is None. 
initial : [scalar, optional] Starting value of the sum. 
Return : Sum of the array elements (a scalar value if axis is none) or array with sum values along the specified axis.

Code #1:

Python3

# Python Program illustrating
# numpy.sum() method
import numpy as np

# 1D array
arr = [20, 2, .2, 10, 4]

print("\nSum of arr : ", np.sum(arr))

print("Sum of arr(uint8) : ", np.sum(arr, dtype = np.uint8))
print("Sum of arr(float32) : ", np.sum(arr, dtype = np.float32))

print ("\nIs np.sum(arr).dtype == np.uint : ",
       np.sum(arr).dtype == np.uint)

print ("Is np.sum(arr).dtype == np.float : ",
       np.sum(arr).dtype == np.float)

Output:

Sum of arr :  36.2
Sum of arr(uint8) :  36
Sum of arr(float32) :  36.2

Is np.sum(arr).dtype == np.uint :  False
Is np.sum(arr).dtype == np.float :  True

Code #2:

Python3

# Python Program illustrating
# numpy.sum() method
import numpy as np

# 2D array
arr = [[14, 17, 12, 33, 44],
       [15, 6, 27, 8, 19],
       [23, 2, 54, 1, 4,]]

print("\nSum of arr : ", np.sum(arr))

print("Sum of arr(uint8) : ", np.sum(arr, dtype = np.uint8))
print("Sum of arr(float32) : ", np.sum(arr, dtype = np.float32))

print ("\nIs np.sum(arr).dtype == np.uint : ",
                 np.sum(arr).dtype == np.uint)

print ("Is np.sum(arr).dtype == np.float : ",
              np.sum(arr).dtype == np.float)

Output:

Sum of arr :  279
Sum of arr(uint8) :  23
Sum of arr(float32) :  279.0

Is np.sum(arr).dtype == np.uint :  False
Is np.sum(arr).dtype == np.float :  False

Code #3:

Python3

# Python Program illustrating
# numpy.sum() method

import numpy as np

# 2D array
arr = [[14, 17, 12, 33, 44],
       [15, 6, 27, 8, 19],
       [23, 2, 54, 1, 4,]]

print("\nSum of arr : ", np.sum(arr))
print("Sum of arr(axis = 0) : ", np.sum(arr, axis = 0))
print("Sum of arr(axis = 1) : ", np.sum(arr, axis = 1))

print("\nSum of arr (keepdimension is True): \n",
      np.sum(arr, axis = 1, keepdims = True))

Output:

Sum of arr :  279
Sum of arr(axis = 0) :  [52 25 93 42 67]
Sum of arr(axis = 1) :  [120  75  84]

Sum of arr (keepdimension is True): 
 [[120]
 [ 75]
 [ 84]]