Reading text file and assigning it to a variable in Python

Question

I am trying to read a text file, which has the following structure:

BUS 0   
0   1   2   3   
0   4   1   9   2   3   
BUS 1  
0   1   9   2   3   
0   1   2   3   
0   1   2   3

It is basically a 3D list, where the nested 2D lists are matrices with an unequal number of columns and rows. The first index is denoted by the string "BUS", followed by a number. The next lines are correspond to a 2D list, with each line being a list, until the next "BUS" string. I need to assign the numbers in this text file to a 3D list in Python. The example given above should translate to :

[ [ [0,1,2,3],[0,4,1,9,2,3] ], [ [0,1,9,2,3],[0,1,2,3],[0,1,2,3] ] ]

Thanks in advance for any help.

Does this answer your question? How to read data from a text file in Python? — Shashikant R. Dhuppe
– Shashikant R. Dhuppe, Commented Oct 26, 2021 at 17:48

user2390182 · Accepted Answer · 2021-10-26 15:45:58Z

0

You can try the following:

data = []

with open("file.wtv") as file_in:
    for line in file_in:
        try:
            row = [*map(int, line.strip().split())]
            data[-1].append(row)
        except ValueError:
            data.append([])

data
# [[[0, 1, 2, 3], [0, 4, 1, 9, 2, 3]], 
#  [[0, 1, 9, 2, 3], [0, 1, 2, 3], [0, 1, 2, 3]]]

answered Oct 26, 2021 at 15:45

user2390182

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3 Comments

pho Over a year ago

Instead of answering questions that demonstrate no effort on OP's part, I'd suggest a better strategy to deal with such questions is to add a comment pointing them in the right direction, and flag to close. Giving OP the code they are asking for doesn't help them because they won't learn, and it doesn't help the community because it encourages more basic questions without showing their research/coding effort.

user2390182 Over a year ago

It's you, sheriff? :D (anonymized my profile) But of course you are right. I can understand, however, that sometimes as a beginner you don't know where to start.

David Galarza Over a year ago

Thanks! This did the trick!

mozway · Accepted Answer · 2021-10-26 15:46:46Z

0

You need to write a simple parser:

test = '''BUS 0
0 1 2 3
0 4 1 9 2 3
BUS 1
0 1 9 2 3
0 1 2 3
0 1 2 3'''

out = []
for line in test.split('\n'):
    if line.startswith('BUS'):
        out.append([])
    else:
        out[-1].append(list(map(int, line.split())))

output:

[[[0, 1, 2, 3], [0, 4, 1, 9, 2, 3]],
 [[0, 1, 9, 2, 3], [0, 1, 2, 3], [0, 1, 2, 3]]]

from a file:

with open('file.txt') as f:
    out = []
    for line in f:
        if line.startswith('BUS'):
            out.append([])
        else:
            out[-1].append(list(map(int, line.split())))

answered Oct 26, 2021 at 15:46

mozway

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