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我遇到这样一种情况，我有几个项目想使用 with block 打开。就我而言，这些是外部硬件设备，在关闭时需要进行一些清理——但这对当前的问题来说并不重要。
假设一个类是这样的:
class Controller(object):
def __init__(self, name):
self._name = name
def __enter__(self):
# Do some work on entry
print("Entering", self._name)
return self
def __exit__(self, type, value, traceback):
# Clean up (restoring external state, turning off hardware, etc)
print("Exiting", self._name)
return False
def work(self):
print("Working on", self._name)
我会(给定固定数量的 Controller)，做类似的事情
with Controller("thing1") as c1:
with Controller("thing2") as c2:
c1.do_work()
c2.do_work()
但是，我遇到过这样一种情况，我需要以这种方式管理大量的事情。也就是说，我的情况类似于:
things = ["thing1", "thing2", "thing3"] # flexible in size
for thing in things:
with Controller(thing) as c:
c.do_work()
但是，上面的内容并没有完全满足我的需要——即一次性为范围内的所有事物设置Controllers。
我已经构建了一个通过递归工作的玩具示例:
def with_all(controllers, f, opened=None):
if opened is None:
opened = []
if controllers:
with controllers[0] as t:
opened.append(t)
controllers = controllers[1:]
with_all(controllers, f, opened)
else:
f(opened)
def do_work_on_all(controllers):
for c in controllers:
c.work()
names = ["thing1", "thing2", "thing3"]
controllers = [Controller(n) for n in names]
with_all(controllers, do_work_on_all)
但我不喜欢实际函数调用的递归或抽象。我对以更“pythonic”的方式执行此操作的想法很感兴趣。