subprocess 模块允许我们启动一个新进程，并连接到它们的输入/输出/错误管道，从而获取返回值。
communicate(input,timeout): 和子进程交互，发送和读取数据。


import subprocess

res=subprocess.Popen("python",stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
out,err=res.communicate(b"for i in range(100):print(i)")
print(out.decode())
res=subprocess.Popen("python",stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.PIPE)
out,err=res.communicate(b"a=10;b=20;print(a+b)")
print(out.decode())

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