![](/img/trans.png)
[英]Python memoized with **kwargs when calling a function doesn't seem to work
[英]input command doesn't seem to work when used with popen python
我正在编写一个执行scala命令的小型python应用程序。 用户可以通过STDIN插入命令,然后python应用将其转发到scala解释器。 执行命令后,应用程序将显示操作结果。
这个想法是使用Popen
创建一个管道,通过该管道我可以发送命令并读取结果。 这个想法很简单,但是没有用。 我不明白的是,为什么在打开管道后sys.stdin
不再起作用。 这使得无法在python中读取命令。
这是我正在使用的代码:
import sys
from subprocess import Popen, PIPE
with Popen(["scala"], stdout=PIPE, stdin=PIPE, bufsize=0, universal_newlines=True) as scala:
while True:
print("Enter scala command >>> ", end="")
sys.stdout.flush()
command = input()
scala.stdin.write(command)
scala.stdin.flush()
print(scala.stdout.readline())
您需要从scala启动时开始读取所有行,然后用新行输入命令,并在获得以下两行输出之后:
from subprocess import Popen, PIPE
with Popen(["scala"], stdout=PIPE, stdin=PIPE, bufsize=0, universal_newlines=True) as scala:
for line in scala.stdout:
print(line)
if not line.strip():
break
while True:
command = input("Enter scala command >>> \n")
scala.stdin.write(command+"\n")
scala.stdin.flush()
for line in scala.stdout:
if not line.strip():
break
print(line)
运行示例:
Welcome to Scala version 2.11.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_60).
Type in expressions to have them evaluated.
Type :help for more information.
Enter scala command >>> 3+4
scala> 3+4
res0: Int = 7
Enter scala command >>> 4 * 4
scala> 4 * 4
res1: Int = 16
Enter scala command >>> 16 / 4
scala> 16 / 4
res2: Int = 4
为了使它能够通过使用不带缓冲区的 bash运行,似乎可以解决输出问题:
from subprocess import Popen, PIPE
with Popen(["unbuffer", "-p","scala"], stdout=PIPE, stdin=PIPE, bufsize=0, universal_newlines=True) as scala:
for line in scala.stdout:
print(line)
if not line.strip():
break
while True:
command = input("Enter scala command >>> ")
scala.stdin.write(command+"\n")
scala.stdout.flush()
for line in scala.stdout:
if not line.strip():
break
print(line)
如果您使用的是Mac Os x,则可能应该使用:
with Popen(["script", "-q", "/dev/null", "scala"], stdout=PIPE, stdin=PIPE, bufsize=0, universal_newlines=True) as scala:
从bash:
print(line)
## -- End pasted text --
Welcome to Scala version 2.11.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_60).
Type in expressions to have them evaluated.
Type :help for more information.
Enter scala command >>> 4 + 2
scala> 4 + 2
res0: Int = 6
Enter scala command >>> 4 * 12
scala> 4 * 12
res1: Int = 48
Enter scala command >>> 100 // 25
scala> 100 // 25
res2: Int = 100
Enter scala command >>>
有关外壳缓冲区问题的更多信息:
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.