| Tim Peters | 400cbc3 | 2006-02-28 18:44:41 +0000 | [diff] [blame] | 1 | import sys |
| 2 | from collections import deque |
| 3 | |
| 4 | |
| 5 | class nested(object): |
| 6 | def __init__(self, *contexts): |
| 7 | self.contexts = contexts |
| 8 | self.entered = None |
| 9 | |
| 10 | def __context__(self): |
| 11 | return self |
| 12 | |
| 13 | def __enter__(self): |
| 14 | if self.entered is not None: |
| 15 | raise RuntimeError("Context is not reentrant") |
| 16 | self.entered = deque() |
| 17 | vars = [] |
| 18 | try: |
| 19 | for context in self.contexts: |
| 20 | mgr = context.__context__() |
| 21 | vars.append(mgr.__enter__()) |
| 22 | self.entered.appendleft(mgr) |
| 23 | except: |
| 24 | self.__exit__(*sys.exc_info()) |
| 25 | raise |
| 26 | return vars |
| 27 | |
| 28 | def __exit__(self, *exc_info): |
| 29 | # Behave like nested with statements |
| 30 | # first in, last out |
| 31 | # New exceptions override old ones |
| 32 | ex = exc_info |
| 33 | for mgr in self.entered: |
| 34 | try: |
| 35 | mgr.__exit__(*ex) |
| 36 | except: |
| 37 | ex = sys.exc_info() |
| 38 | self.entered = None |
| 39 | if ex is not exc_info: |
| 40 | raise ex[0], ex[1], ex[2] |