numpy.sum(arr，axis，dtype，out)：此函数返回指定轴上的数组元素之和。
参数：
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.返回： Sum of the array elements (a scalar value if axis is none) or array with sum values along the specified axis.
代码1：
# 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.uint:",
np.sum(arr).dtype == np.float) 输出：
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.uint: True
代码2：
# 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.uint:",
np.sum(arr).dtype == np.float) 输出：
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.uint: False
代码3：
# 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))输出：
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]]
相关用法
注：本文由纯净天空筛选整理自Mohit Gupta_OMG 大神的英文原创作品 numpy.sum() in Python。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。