Exercise: A line from a file

We want to read lines from one of more files. We want each line to

• be a string
• have a filename attribute
• have a linenumber attribute

Recall that we can already iterate over the lines of a file.

The interface I suggest is

filename = 'myfile.txt'
f = open(filename)
labelled_lines = LabelledLines(f, filename)

The behavior we’d like is for this code

for line in labelled_lines:
    print (line.filename, line.linenumber, line)

to produce output like

('myfile.txt', 0, 'First line\n')
('myfile.txt', 1, 'Second line\n')
('myfile.txt', 2, 'Third line\n')