Converting and organizing a .txt file into a list to compare to another .txt file

Question

I am trying to read two test files and compare their data in python. the text files look like:

x y
x y
x y
x y

and I am trying to compare the values of x in both lists and then see if they have the same y values. I'm not too stuck on the comparing part, but I can't understand how to turn the text files into a pair of lists that would be able to be compared.

I know I should be stripping the lines like so

with open('xy.txt', 'r') as f:
    xy = [line.strip() for line in f]

but I don't know how to sort them so I could sort them with an algorithm afterward. Any help would be greatly appreciated!

Answer 1

The code:

with open('xy.txt', 'r') as f:
    xy = [line.strip() for line in f]

# Take the list of strings, where integers separated by space, and make a list of tuples of integers.
# For each line, separate on spaces, cast each to integer, and put in tuple.
lst = [(int(s.split(" ")[0]), int(s.split(" ")[1])) for s in xy]
print("Unsorted:", lst)

# Sort the list of tuples, using the first element then the second.
# Taken from: https://stackoverflow.com/questions/9376384/sort-a-list-of-tuples-depending-on-two-elements
lst = sorted(lst, key=lambda element: (element[0], element[1]))

print("Sorted:", lst)

The test textfile:

4 6
111 2
7 3
4 4
6 4

The output:

Unsorted: [(4, 6), (111, 2), (7, 3), (4, 4), (6, 4)]
Sorted: [(4, 4), (4, 6), (6, 4), (7, 3), (111, 2)]

See also this post.

Answer 2

A beginning example:

# Contents xy.txt
a 1
d 3
b 2
c 4

with open('xy.txt', 'r') as f:
    xy = [line.strip().split() for line in f]

xy                                                                                                                                                                                                                      
[['a', '1'], ['d', '3'], ['b', '2'], ['c', '4']]

xy.sort()                                                                                                                                                                                                               
xy                                                                                                                                                                                                                      
['a', '1'], ['b', '2'], ['c', '4'], ['d', '3']]

sort() has argument key=some_func. You can create a function that does custom sorting:

def y_sort(e): 
    return e[1] 

xy.sort(key=y_sort)                                                                                                                                                                                                     

xy                                                                                                                                                                                                                      
[['a', '1'], ['b', '2'], ['d', '3'], ['c', '4']]