Question

我可以将第0列中的项目加总。但是我在哪里将代码更改为矩阵中的第2列，第3列或第4列的总和？我很容易难倒。

def main():
    matrix = []

    for i in range(2):
        s = input("Enter a 4-by-4 matrix row " + str(i) + ": ") 
        items = s.split() # Extracts items from the string
        list = [ eval(x) for x in items ] # Convert items to numbers   
        matrix.append(list)

    print("Sum of the elements in column 0 is", sumColumn(matrix))

def sumColumn(m):
    for column in range(len(m[0])):
        total = 0
        for row in range(len(m)):
            total += m[row][column]
        return total

main()

Answer 1

numpy可以很容易地为你做到这一点：

def sumColumn(matrix):
    return numpy.sum(matrix, axis=1)  # axis=1 says "get the sum along the columns"

当然，如果您想手动完成，请按照以下方法修改代码：

def sumColumn(m):
    answer = []
    for column in range(len(m[0])):
        t = 0
        for row in m:
            t += row[column]
        answer.append(t)
    return answer

仍然有一种更简单的方法，使用zip：

def sumColumn(m):
    return [sum(col) for col in zip(*m)]

Answer 2

一衬垫：

column_sums = [sum([row[i] for row in M]) for i in range(0,len(M[0]))]

也

row_sums = [sum(row) for row in M]

对于任何矩形非空矩阵（列表列表）M。 e.g。

>>> M = [[1,2,3],\
>>>     [4,5,6],\
>>>     [7,8,9]]
>>>
>>> [sum([row[i] for row in M]) for i in range(0,len(M[0]))]
[12, 15, 18] 
>>> [sum(row) for row in M]
[6, 15, 24]

Answer 3

要获取矩阵中所有列的总和，可以使用以下python numpy代码：

matrixname.sum(axis=0)

Answer 4

如果将矩阵表示为平面数组，这可以更容易：

m = [
    1,2,3,4,
    10,11,12,13,
    100,101,102,103,
    1001,1002,1003,1004
]

def sum_column(m, n):
    return sum(m[i] for i in range(n, 4 * 4, 4))

Answer 5

以下代码已更改为返回指定列的总和：

def sumColumn(m, column):
    total = 0
    for row in range(len(m)):
        total += m[row][column]
    return total

column = 1
print("Sum of the elements in column", column, "is", sumColumn(matrix, column))

Answer 6

import numpy as np
np.sum(M,axis=1)

其中M是矩阵

python中的sum矩阵列

6 个答案: