How to take input through text file in python?

Question

enter code here

def prims():

  r = 4;
  c = 4;
  total = 0
  matrix = [ [0 for x in range(r)] for y in range(c)]
  min = 999
  u = 0
  v = 0
  visited = [None]*4
  for i in range(0,4):
    visited[i] = 0
    for j in range(0,4):
        matrix[i][j] = input()
        if matrix[i][j]== 0:
            matrix[i][j] = 999
 visited[0] = 1
 for counter in range(0,3):
    min = 999
    for  i in range(0,4):
        if visited[i] == 1:
            for j in range(0,4):
                if visited[j] != 1:
                    if min > matrix[i][j]:
                        min = matrix[i][j]
                        a = u = i
                        b = v = j
    visited[v] = 1
    total = total + min

    print("edge found :{}->{}:{}".format(u,v,min))
print("The weight of minimum spanning tree is : {}".format(total))
return

prims()

What I have to do, if I want go give input as text file to this program. I have created a file named "input.txt".There I put inputs of matrix. Can anyone help me with solution please.

input.txt :

0 28 999 999 999 10 999

28 0 16 999 999 999 14

999 16 0 12 999 999 999

999 999 12 0 22 999 18

999 999 999 22 0 25 24

10 999 999 999 25 0 999

999 14 999 18 24 999 999

How your program is reading the inputs? I couldn't see. But if at all, you can get the file content read into a variable as "inputs = [int(i) for i in open('input.txt', 'r').read().split(' ')]" — Vivek Harikrishnan
– Vivek Harikrishnan, Commented Nov 28, 2017 at 11:21
If you input is spanning over multiple lines then, something like this "inputs = [int(line.strip()) for lines in open('input.txt', 'r').readlines() for line in lines.split(' ')]" — Vivek Harikrishnan
– Vivek Harikrishnan, Commented Nov 28, 2017 at 11:26

jo9k · Accepted Answer · 2017-11-28 12:11:17Z

2

Here is the way to read from file

file = open('path of input file')
for line in file.readlines():
  print(list(map(int, line.split(' '))))
file.close()

you can store it to an array as well by doing

arr = []
file = open('path of input file')
for line in file.readlines():
  arr.append(list(map(int, line.split(' '))))
print(arr)
file.close()

output is

[[0, 28, 999, 999, 999, 10, 999], [28, 0, 16, 999, 999, 999, 14], [999, 16, 0, 12, 999, 999, 999], [999, 999, 12, 0, 22, 999, 18], [999, 999, 999, 22, 0, 25, 24], [10, 999, 999, 999, 25, 0, 999], [999, 14, 999, 18, 24, 999, 999]]

edited Nov 28, 2017 at 12:11

jo9k

7106 silver badges19 bronze badges

answered Nov 28, 2017 at 11:45

sujit tiwari

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Comments

jo9k · Accepted Answer · 2017-11-28 11:57:42Z

If I understand correctly, you are looking for a way to transform input such as:

0 28 999 999 999 10 999
28 0 16 999 999 999 14
999 16 0 12 999 999 999
999 999 12 0 22 999 18
999 999 999 22 0 25 24
10 999 999 999 25 0 999
999 14 999 18 24 999 999

Which you get from file, into matrix ixj.

matrix = []
with open('test.txt') as file:
    for line in file:
        matrix.append([int(val) for val in line.split()])

You get result:

matrix
Out[93]: 
[[0, 28, 999, 999, 999, 10, 999],
 [28, 0, 16, 999, 999, 999, 14],
 [999, 16, 0, 12, 999, 999, 999],
 [999, 999, 12, 0, 22, 999, 18],
 [999, 999, 999, 22, 0, 25, 24],
 [10, 999, 999, 999, 25, 0, 999],
 [999, 14, 999, 18, 24, 999, 999]]

And of course you can use indexing:

matrix[1][2]
Out[94]: 16

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