Python: readlines()-method creates empty lists

Question

I'm trying to parse items from a text file with lines of text separated by semicolons like this:

4037;HKO_2005;OBJECT-ORIENTED PROGRAMMING               ;18.12.2011;5

4037;HKO_2009;DATABASES I                               ;2.5.2011;5

4037;HKO_2011;ALGORITHMS I                              ;7.5.2011;5

4037;HKO_2038;PROGRAMMING BASICS IN JAVA                ;22.5.2010;5

to a list of lists like this:

['4037', 'HKO_2005', 'OBJECT-ORIENTED PROGRAMMING', '18.12.2011', '5'],
['4037', 'HKO_2009', 'DATABASES I', '2.5.2011', '5'],
['4037', 'HKO_2011', 'ALGORITHMS I', '7.5.2011', '5'],
['4037', 'HKO_2038', 'PROGRAMMING BASICS IN JAVA', '22.5.2010', '5']

Right now the code I'm using for testing looks like this:

class Main:
    def inputFile(self):
        with open('data.txt', 'r') as data:
            self.stuff = data.readlines()
            self.separate = [elem.strip().split(';') for elem in self.stuff]
            print(self.separate)

justdoit = Main()
justdoit.inputFile()

My problem is what you already saw: the text file didn't look to have double newlines until I pasted it here. Using my code the readlines()-method creates empty lists in between with the newlines like this:

['4037', 'HKO_2005', 'OBJECT-ORIENTED PROGRAMMING          ', '18.12.2011', '5'],
[''],
['4037', 'HKO_2009', 'DATABASES I                          ', '2.5.2011', '5'],
[''],
['4037', 'HKO_2011', 'ALGORITHMS I                         ', '7.5.2011', '5'],
[''],
['4037', 'HKO_2038', 'PROGRAMMING BASICS IN JAVA           ', '22.5.2010', '5']
['']

I believe I can later strip the blanks from the course names with rstrip(), but the newlines are giving me a headache. Earlier I was getting an IndexError because of this and I had no idea the text file had double newlines. How can I effectively ignore or remove these extra newlines before the lists are created?

Answer 1

You can add a condition to the list comprehension:

self.separate = [elem.strip().split(';') for elem in self.stuff if elem.strip()]