def reverse_lines(n):
    with open(n,'r') as fie:
        data = fie.read().split('\n')
        if len(data)== 0:
            pass
        else:    
            print(data[0])
            ding = data[1::]
            fie = '\n'.join(ding)
    file(n).truncate()
    file(n).write(fie)
           
    return reverse_lines(n)

I am struggling to write to the file because I only have the file name. I do not understand the interaction between what I return and the parameter it accepts.

CodePudding user response：

This answer I consider poor because it abuses the parameters and also manually catches a StopIteration. Still it is recursive and produces the correct output:

def reverse_lines(n, contents = None):
    if not contents:
        with open(n, 'r') as file:
            contents = (line.strip() for line in file)
            reverse_lines(n, contents)
    else:
        try:
            line = next(contents)
            reverse_lines(n, contents)
            print(line)
        except StopIteration:
            pass
        
reverse_lines('poem.txt')

Output as requested.

CodePudding user response：

My approach would be to make a lines generator that generates the lines of a given filename -

def lines(filename):
  with open(filename) as f:
    for line in f:
      yield line.strip()

And a generic reverse generator that reverses any iterable, it -

def reverse(it):
  stop = {}
  v = next(it, stop)
  if v is stop: return
  yield from reverse(it)
  yield v

Combine them for the desired effect -

for line in reverse(lines("myfile.txt")):
  print(line)

Given myfile.txt -

a
b
c
d
e
f
g

Output -

g
f
e
d
c
b
a