python - Decorators influencing sys._getframe(1) -

a.py

import d  d.funcme('blah') 

d.py

import sys import errors def argcheck(in_=(), out=(type(none),)):     def _argcheck(function):         # here         def __argcheck(*args, **kw):             print '+++++++++ checking types before calling func'             # here             res = function(*args, **kw)             return res         return __argcheck     return _argcheck  @argcheck((str))       <----- def funcme(name):     try:         f = sys._getframe(1)     except valueerror, err:         raise errors.usererror(err)     # stack deep         filename, lineno = f.f_globals['__name__'], f.f_lineno     print filename, lineno 

output without argcheck decorator (comment out @argcheck((str))):

$ python a.py   __main__ 3   

output argcheck decorator:

$ python a.py   +++++++++ checking types before calling func   defines 9   

questions:

1. what's decorator doing it's changing values _getframe?

2. how can preserve information captures original information i.e __main__ 3 , not defines 9?

the problem yourfuncme()function assuming has been called directly rather indirectly through else — such decorator. fixed changing calling sequence , adding additionaldepthkeyword argument default value passed on _sys._getframe(). scaffolding in place, decorator can override default value. following print same thing whether or not decorator has been applied:

 1 import sys  2 import errors  3 def argcheck(in_=(), out=(type(none),)):  4     def _argcheck(function):  5         # here  6         def __argcheck(*args, **kw):  7             print '+++++++++ checking types before calling func'  8             # here  9             res = function(*args, depth=2, **kw)  # override default depth 10             return res 11         return __argcheck 12     return _argcheck 13 14 @argcheck((str)) 15 def funcme(name, depth=1):  # added keyword arg default value 16     try: 17         f = sys._getframe(depth)   # explicitly pass stack depth wanted 18     except valueerror, err: 19         raise errors.usererror(err)     # stack deep 20 21     filename, lineno = f.f_globals['__name__'], f.f_lineno 22     print filename, lineno