Difference between two list

Question

I have the following text file:

text1 text2
# text2 text3 text4
# text5 text4 text6
text 3 text 4
# ....
...

I would like to have a array list like the following, where fu

dict[function([text1, text2])] = [[text2, text3, text4], [text5, text4, text6]].

The idea is to open the file, read line by line

dict = {}
inputfile = open("text.txt","r")
for line in inputfile:
    l=line.split()
if not line.startswith("#"):
#create a new key
else: 
dict[key] = l

However, the problem is that I cannot assign other element if I go to the next line. Do you know how to solve this issue?

"Function"is just a function which I defined elsewhere and that takes as an input a list of strings.

Answer 1

You can use collections.defaultdict to create a dictionary with list s as the values to which you can append items.

from collections import defaultdict

my_dict = defaultdict(list)

with open('text.txt') as f:
    key = ''
    for line in f:
        if not line.startswith('#'):
            key = line
            # key = function(line.split())
            continue
        my_dict[key].append(line.strip('#').split())

print(my_dict)

Output:

defaultdict(<class 'list'>,
            {'text1 text2\n': [['text2', 'text3', 'text4'],
                               ['text5', 'text4', 'text6']],
             'text3 text4\n': [['text21', 'text31', 'text41'],
                               ['text51', 'text41', 'text61']]})

Just change the key = line line to whatever function you're passing the key to.

My text.txt file contains:

text1 text2
# text2 text3 text4
# text5 text4 text6
text3 text4
# text21 text31 text41
# text51 text41 text61