计算 2D NumPy 数组中所有列的总和
让我们看看如何计算 2D NumPy 数组中所有列的总和。 方法 1 : 使用嵌套循环按列访问数组元素，然后将它们的和存储在变量中，然后打印出来。 例 1:
Python 3
# importing required libraries
import numpy
# explicit function to compute column wise sum
def colsum(arr, n, m):
for i in range(n):
su = 0;
for j in range(m):
su += arr[j][i]
print(su, end = " ")
# creating the 2D Array
TwoDList = [[1, 2, 3], [4, 5, 6],
[7, 8, 9], [10, 11, 12]]
TwoDArray = numpy.array(TwoDList)
# displaying the 2D Array
print("2D Array:")
print(TwoDArray)
# printing the sum of each column
print("\nColumn-wise Sum:")
colsum(TwoDArray, len(TwoDArray[0]), len(TwoDArray))
输出:
2D Array:
[[ 1 2 3]
[ 4 5 6]
[ 7 8 9]
[10 11 12]]
Column-wise Sum:
22 26 30
例 2 :
Python 3
# importing required libraries
import numpy
# explicit function to compute column wise sum
def colsum(arr, n, m):
for i in range(n):
su = 0;
for j in range(m):
su += arr[j][i]
print(su, end = " ")
# creating the 2D Array
TwoDList = [[1.2, 2.3], [3.4, 4.5]]
TwoDArray = numpy.array(TwoDList)
# displaying the 2D Array
print("2D Array:")
print(TwoDArray)
# printing the sum of each column
print("\nColumn-wise Sum:")
colsum(TwoDArray, len(TwoDArray[0]), len(TwoDArray))
输出:
2D Array:
[[1.2 2.3]
[3.4 4.5]]
Column-wise Sum:
4.6 6.8
方法 2: 使用 NumPy，numpy.sum(arr，axis，dtype，out)函数中的 sum() 函数返回指定轴上数组元素的和。要计算所有列的总和，sum()函数中的 axis 参数应为 0。 例 1 :
Python 3
# importing required libraries
import numpy
# creating the 2D Array
TwoDList = [[1, 2, 3], [4, 5, 6],
[7, 8, 9], [10, 11, 12]]
TwoDArray = numpy.array(TwoDList)
# displaying the 2D Array
print("2D Array:")
print(TwoDArray)
# printing the sum of each column
print("\nColumn-wise Sum:")
print(numpy.sum(TwoDArray, axis = 0))
输出:
2D Array:
[[ 1 2 3]
[ 4 5 6]
[ 7 8 9]
[10 11 12]]
Column-wise Sum:
22 26 30
例 2 :
Python 3
# importing required libraries
import numpy
# creating the 2D Array
TwoDList =[[1.2, 2.3], [3.4, 4.5]]
TwoDArray = numpy.array(TwoDList)
# displaying the 2D Array
print("2D Array:")
print(TwoDArray)
# printing the sum of each column
print("\nColumn-wise Sum:")
print(*numpy.sum(TwoDArray, axis = 0))
输出:
2D Array:
[[1.2 2.3]
[3.4 4.5]]
Column-wise Sum:
4.6 6.8
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