如何抽象标准输入/标准输出和文件？

Question

I'm trying to write a Python script which lets the user to switch between stdin/stdout and files for input/output. But I'm not sure if my implementation is correct:

#!/usr/bin/python3

import fileinput
import sys

from contextlib import contextmanager
from contextlib import redirect_stdout


def foo(file):
    return ''.join([line for line in file])


@contextmanager
def run(input_file, output_file):
    stdin = '-' if input_file is None else input_file
    stdout = sys.stdout if output_file is None else open(output_file, 'w')
    with fileinput.input(stdin) as stdin, stdout:
        with redirect_stdout(stdout):
            print(foo(stdin))

1. Is the code managing resources correctly?
2. How can I properly handle character encoding? I'd like to have everything in utf-8.
3. Is there any room for improvement in the above code?

Answer 1

I think you would need to do this way. You don't need to make run() itself a @contextmanager —all it needs to do is use one (or more, and both fileinput.input and redirect_stdout are ones already). I'm not sure why you're using fileinput.input since there appears to only be one input file involved.

from contextlib import redirect_stdout
import fileinput
import sys

def foo(file):
    return ''.join([line for line in file])

def run(input_file, output_file):
    stdin = '-' if input_file is None else input_file
    stdout = sys.stdout if output_file is None else open(output_file, 'w')
    with fileinput.input(stdin) as stdin, redirect_stdout(stdout):
        print(foo(stdin))

run('input.txt', 'output.txt')
run('input.txt', None)