Question

I am copying this answer like this

for line in fileinput.input(['my_file'], inplace=True):
    sys.stdout.write('_____ {l}'.format(l=line))

to add four underlines to beginning of line. This turns my_file into a checklist. But the above code prints the underlines on the blank lines too. I want to change the blank lines to full length lines. How do I do that? So if the original lines are like this

abc

def

ghi

the checklist will look like

___ abc

_________________________________________________

___ def

_________________________________________________

___ ghi

_________________________________________________

---

Thanks!

Answer 1

Strip the whitespace on the line and see if it’s non-empty (and thus, truthy). If it’s non-empty, do what it did before. Otherwise, it’s empty; print the horizontal line. (although I must say 49 characters is somewhat odd)

term_width = 50
with contextlib.closing(fileinput.input(['my_file'], inplace=True)) as f:
    for line in f:
        if line.strip():
            sys.stdout.write('_____ {l}'.format(l=line))
        else:
            sys.stdout.write('\n'.rjust(term_width, '_'))