ScopeExit.py

class ScopeExit:
    def __init__(self, revert_exec=False):
        self.revert_exec = revert_exec
        self.cbs = []

    def add_cb(self, cb):
        self.cbs.append(cb)

    def del_cb(self, cb):
        used = 0
        for cbx in self.cbs:
            if cb == cbx:
                continue
            self.cbs[used] = cbx
            used += 1
        self.cbs = self.cbs[:used]

    def __enter__(self):
        pass

    def __exit__(self, type, value, traceback):
        if self.revert_exec:
            self.cbs.reverse()
        for cb in self.cbs:
            cb()

def demo():
    tool = ScopeExit(True)
    cb1 = lambda: print('step1 exec')
    cb2 = lambda: print('step2 exec')
    tool.add_cb(cb1)
    tool.add_cb(cb2)
    tool.del_cb(cb1)
    with tool:
        print("begin")
        return
    print("end")