1 #!/usr/bin/env python 2 # Copyright (c) 2012 The Chromium Authors. All rights reserved. 3 # Use of this source code is governed by a BSD-style license that can be 4 # found in the LICENSE file. 5 6 '''In GRIT, we used to compile a lot of regular expressions at parse 7 time. Since many of them never get used, we use lazy_re to compile 8 them on demand the first time they are used, thus speeding up startup 9 time in some cases. 10 ''' 11 12 import re 13 14 15 class LazyRegexObject(object): 16 '''This object creates a RegexObject with the arguments passed in 17 its constructor, the first time any attribute except the several on 18 the class itself is accessed. This accomplishes lazy compilation of 19 the regular expression while maintaining a nearly-identical 20 interface. 21 ''' 22 23 def __init__(self, *args, **kwargs): 24 self._stash_args = args 25 self._stash_kwargs = kwargs 26 self._lazy_re = None 27 28 def _LazyInit(self): 29 if not self._lazy_re: 30 self._lazy_re = re.compile(*self._stash_args, **self._stash_kwargs) 31 32 def __getattribute__(self, name): 33 if name in ('_LazyInit', '_lazy_re', '_stash_args', '_stash_kwargs'): 34 return object.__getattribute__(self, name) 35 else: 36 self._LazyInit() 37 return getattr(self._lazy_re, name) 38 39 40 def compile(*args, **kwargs): 41 '''Creates a LazyRegexObject that, when invoked on, will compile a 42 re.RegexObject (via re.compile) with the same arguments passed to 43 this function, and delegate almost all of its methods to it. 44 ''' 45 return LazyRegexObject(*args, **kwargs) 46
