Making a function where you read from another file in Python | Solution

 You will have write it like this: dictionary[key] = value instead of using append

readlines() seems to be useful in your case to, since you only

def data(name):
    input_file = open(name, 'r')
    di = {}
    for line in input_file.readlines():
        fields = line.split()
        read_name = fields[0]
        read_seq = fields[1]
        di[read_name] = read_seq

    input_file.close()
    return di


print(data('sequences.txt'))

Another thing is that the code after your return statement won't run. An easy way to fix this is to write it before the statement, or use a context manager, which automatically closes the file for you. This code does the same, but is shorter, and I would way easier to read, which is always a good thing.

def data(name):
    di = {}
    with open(name, 'r') as file:
        for line in file.readlines():
            read_name, read_seq = line.split()
            di[read_name] = read_seq
    return di


print(data('sequences.txt'))