Txt file python unique values

Question

So I have a txt file with many lines that look like this:

2107|Business|2117|Art|2137|Art|2145|English

Essentially it is a random students major and an encoded semester and year that they declared it before it. What I want to be able to do is read in the semester each unique major was declared initially. From the line above I would need:

2107:Business

2117: Art

2145: English

I was attempting to do this with Pandas in Python but really can't get anything to work. Any help appreciated?

EDIT: Should have clarified. I don't want the code to read in the second instance of Art. Only the first declaration and semester before for each major.

Answer 1

Use Python's CSV library to help with splitting each of the rows into a list of cells. You can then make use of Python's grouper() recipe which is used to take n items at a time out of a list:

import csv
import itertools

def grouper(iterable, n, fillvalue=None):
    "Collect data into fixed-length chunks or blocks"
    # grouper('ABCDEFG', 3, 'x') --> ABC DEF Gxx
    args = [iter(iterable)] * n
    return itertools.izip_longest(fillvalue=fillvalue, *args)

seen = set()

with open('input3.txt', 'rb') as f_input:
    for row in csv.reader(f_input, delimiter='|'):
        for k, v in grouper(row, 2):
            if v not in seen:
                print "{}: {}".format(k, v)
                seen.add(v)

So for your example file line, this would give you:

2107: Business
2117: Art
2145: English