Python includes exercises 38

Python 100 Li

Topic: seeking a 3 * 3 matrix diagonal elements sum.

Program analysis: the use of a double for loop control input two-dimensional array, then a [i] [i] after cumulative output.

Source Code:

#!/usr/bin/python
# -*- coding: UTF-8 -*-

if __name__ == '__main__':
    a = []
    sum = 0.0
    for i in range(3):
        a.append([])
        for j in range(3):
            a[i].append(float(raw_input("input num:\n")))
    for i in range(3):
        sum += a[i][i]
    print sum

The above example output is:

input num:
78
input num:
34
input num:
23
input num:
34
input num:
56
input num:
33
input num:
12
input num:
21
input num:
2
136.0

Python 100 Li