Popen在几次互动后停止工作

Question

我正在尝试使用subprocess.Popen class与外部程序进行交互。外部程序接受输入并返回输出。我正在关注here中的示例，但似乎Popen在几次互动后停止工作。这是一个例子：

这是test.sh

的代码

# test.sh
#!/bin/bash
while true; do
echo Hello, who am I talking to?
read varname
echo It\'s nice to meet you $varname
done

在python 3中运行此代码

import subprocess
import io
print('One line at a time:')
proc = subprocess.Popen(
    'test.sh',
    stdin=subprocess.PIPE,
    stdout=subprocess.PIPE
)
stdin = io.TextIOWrapper(
    proc.stdin,
    encoding='utf-8',
    line_buffering=True,  # send data on newline
)
stdout = io.TextIOWrapper(
    proc.stdout,
    encoding='utf-8',
)
for i in range(5):
    line = '{}\n'.format(i)
    stdin.write(line)
    time.sleep(1)
    output = stdout.readline()
    print(output.rstrip())
remainder = proc.communicate()[0].decode('utf-8')
print(remainder)

这是我得到的输出：

One line at a time:
Hello, who am I talking to?
It's nice to meet you 0
Hello, who am I talking to?
It's nice to meet you 1
Hello, who am I talking to?

该程序在此之后挂起。

那么为什么Popen停止在这个例子中工作？