-1

I have a set of coordinate data (saved in a txt file), like this:

Number  N coordinates   E coordinates   Height  Code
1       5111945.980     444258.900      131.300 C
2       5265566.655     443665.554      110.311 BR  
...

It goes on for several dozen rows like that. What I need done is to switch places of N coordinates with the ones on E coordinates (the header title also, of course) while everything else remains the same. For example, this would be the desired outcome in an output txt file:

Number  E coordinates   N coordinates   Height  Code
1       444258.900      5111945.980     131.300 C
2       443665.554      5265566.655     110.311 BR

For now, I only have the bit for printing out the table data as it shows in txt:

# open the source file
myfile = open("sometext.txt", "r")

# print out the data, to check if output working
for line in myfile:
    print(line)

The data is tab spaced, as far as I can see.

I would like to solve this without external libraries, only default Python and its standard library.

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10
  • Is the data tab-delimited or fixed-width columns like in your example? It should be very easy to find solutions for both problems. Please search before asking. Commented Feb 11, 2023 at 15:31
  • do you have to have a txt file or are you open to other formats as well? and does the columns are always in tab space or some number of spaces or? Commented Feb 11, 2023 at 15:32
  • Are there any limitations on the way this will be achieved? for example libraries you don't want to use Commented Feb 11, 2023 at 15:42
  • 1
    What have you searched for, and what did you find? What have you tried, and how did it fail? Commented Feb 11, 2023 at 16:16
  • 1
    Because if they show us what they searched for we can suggest better search terms. A complication is that 90% of the search hits are for Pandas. Commented Feb 11, 2023 at 16:23

3 Answers 3

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0

Solution with no third-party libraries

rows_to_be_switched = ['Number', 'Code']

def flip(row_to_flip, ind1, ind2):
    tmp = row_to_flip[ind1]
    row_to_flip[ind1] = row_to_flip[ind2]
    row_to_flip[ind2] = tmp
    return row_to_flip


with open('file1.txt', 'r') as file1, open('file2.txt', 'w') as file2:
    data_rows = [row.rstrip('\n') for row in file1.readlines()]
    titles_indices = [data_rows[0].split('\t').index(title) for title in rows_to_be_switched]

    for row in data_rows:
        file2.write('\t'.join(flip(row.split('\t'), *titles_indices) + ['\n']))

Explanation:

  • The rows_to_be_switched is a list of two titles that we flip between.
  • The flip functions flips the indices of the items in a list and returns the new list
  • titles_indices = [data_rows[0].split('\t').index(title) for title in rows_to_be_switched] Detects the indices of the titles, and knows where to flip each two items in a row.
  • We then write each row by joining the items with a tab, as it was the delimiter.
  • Edit thanks to @tripleee - we need to strip the line breaks as it is a part of the string, thus .index() wouldn't find last columns. Then we add the \n back to the end of the line.

Input:

file1.txt

Number  N coordinates   E coordinates   Height  Code
1   5111945.980 444258.900  131.300 C
2   5265566.655 443665.554  110.311 BR

Output:

file2.txt

Number  E coordinates   N coordinates   Height  Code
1   444258.900  5111945.980 131.300 C
2   443665.554  5265566.655 110.311 BR
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5 Comments

This doesn't cope with a data file where the last column needs to be moved. You should strip the line endings and then add them back, or simply use the csv library with tab delimiters.
@tripleee You're correct, I'll try and find a fix for it. Thanks for the comment
@tripleee Fixed :) thanks for the enlightenment, if you see more bugs I would gladly fix, or even delete the answer if necessary.
I see another issue - it adds a line break at the end, not sure if it is that ugly or important as it is being ignored anyways, I will wait for the OP's thoughts if it fulfils his intentions.
@no_hex Yup, works like a charm, that one :)
0

Ok, so one way to accomplish it would be using the pandas library and the StringIO library (Notice that pandas is a library that you need to install with pip install pandas),

As you stated in the comments your txt file is a tab delimiter which means \t is what separates your columns, here is one way to accomplish that:

Import libraries and load your file to a variable:

import pandas as pd 
from io import StringIO

txt_path = dir_path + "/sample_txt_file.txt"
string = ""
with open(txt_path, 'r') as file:
    string = file.read()

With your dummy data the variable string will look like that:

'Number\tN coordinates\tE coordinates\tHeight\tCode\n1 \t5111945.980\t444258.900\t131.300\tC\n2 \t5265566.655\t443665.554\t110.311\tBR'

Read it as a dataframe:

df = pd.read_csv(StringIO(string), sep='\t')

Reorder the column based on the columns you specify:

df = df[['Number', 'E coordinates', 'N coordinates', 'Height', 'Code']]

Note, you can reorder as many of them as you want

And save your data to a new txt file:

df.to_csv(new_txt_path, index=None, sep='\t')

Resulting data will be like that:

Number  E coordinates   N coordinates   Height  Code
1       444258.900      5111945.980     131.300 C
2       443665.554      5265566.655     110.311 BR
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1 Comment

You need to pip install pandas in order to use it, in an antithesis to the OP's comment: "No external libraries, only default Python and it's libraries."
-1

You can also utilize the power of the f-string formatting capability and do the following:

l = 0
for line in myfile:
    sl = [x for x in line.split(' ') if x]
    if l == 0:
        print(line) # prints first line without a swap
    else:
        print(f'{sl[0]:8}{sl[2]:16}{sl[1]:14}{sl[3]:10}{sl[4]:4}')
    l += 1
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1 Comment

Meh, -1. 1. The OP stated it is spaces by tabs. 2. It is not generic to the titles (what if a title is now to 16 characters long?

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