我有一个Python脚本，该脚本使用结构库来测试到多个主机的SSH连接。我想将所有结果收集在一个列表中：
...
import fabric
from fabric.api import *
results = []
@parallel
def test_connection():
global results
try:
run('ls')
results += "%s: SUCCESS" % env.host
except Exception as e:
results += "%s: FAILURE. Exception: %e" % (env.host, e)
if __name__ == '__main__':
tasks.execute(test_connection)
print results
执行脚本时，得到以下信息：
Traceback (most recent call last):
File "./test_ssh.py", line 99, in <module>
tasks.execute(test_connection)
File "/Library/Python/2.7/site-packages/fabric/tasks.py", line 387, in execute
multiprocessing
File "/Library/Python/2.7/site-packages/fabric/tasks.py", line 277, in _execute
return task.run(*args, **kwargs)
File "/Library/Python/2.7/site-packages/fabric/tasks.py", line 174, in run
return self.wrapped(*args, **kwargs)
File "./test_ssh.py", line 96, in test_connection
results += "%s: FAILURE. Exception: %e" % (env.host, e)
UnboundLocalError: local variable 'results' referenced before assignment
我认为这是因为test_connection运行它是自己的上下文，所以它没有访问权限results。
那么，还有其他方法可以收集结果吗？
诀窍是您实际上可以从parallel执行中返回结果：
@parallel
def test_connection():
try:
run('ls')
return True
except Exception:
return False
现在，当您调用任务时，您将获得：
result = execute(test_connection)
results = [ ('HOST %s succeeded' % key) if value else ('HOST %s failed' % key) for key, value in result.items() ]
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