用下划线替换其他文件中的新行（不使用with）

Question

I posted a question yesterday in similar regards to this but didn't quite gauge the response I wanted because I wasn't specific enough. Basically the function takes a .txt file as the argument and returns a string with all \\n characters replaced with an '_' on the same line. I want to do this without using WITH. I thought I did this correctly but when I run it and check the file, nothing has changed. Any pointers?

This is what I did:

def one_line(filename):
    wordfile = open(filename)
    text_str = wordfile.read().replace("\n", "_")
    wordfile.close()
    return text_str

one_line("words.txt")

but to no avail. I open the text file and it remains the same.

The contents of the textfile are:

I like to eat
pancakes every day

and the output that's supposed to be shown is:

>>> one_line("words.txt")
’I like to eat_pancakes every day_’

Answer 1

The fileinput module in the Python standard library allows you to do this in one fell swoop.

import fileinput

for line in fileinput.input(filename, inplace=True):
    line = line.replace('\n', '_')
    print(line, end='')

The requirement to avoid a with statement is trivial but rather pointless. Anything which looks like

with open(filename) as handle:
    stuff

can simply be rewritten as

try:
    handle = open(filename)
    stuff
finally:
    handle.close()

If you take out the try / finally you have a bug which leaves handle open if an error happens. The purpose of the with context manager for open() is to simplify this common use case.

Answer 2

You are missing some steps. After you obtain the updated string, you need to write it back to the file, example below without using with

def one_line(filename):
    wordfile = open(filename)
    text_str = wordfile.read().replace("\n", "_")
    wordfile.close()
    return text_str

def write_line(s):
    # Open the file in write mode
    wordfile = open("words.txt", 'w')

    # Write the updated string to the file
    wordfile.write(s)

    # Close the file
    wordfile.close()

s = one_line("words.txt")
write_line(s)

Or using with

with open("file.txt",'w') as wordfile:

    #Write the updated string to the file
    wordfile.write(s)

Answer 3

with pathlib you could achieve what you want this way:

from pathlib import Path

path = Path(filename)
contents = path.read_text()
contents = contents.replace("\n", "_")
path.write_text(contents)