python中使用sys模板和logging模块获取行号和函数名的方法

对于python,这几天一直有两个问题在困扰我:1.python中没办法直接取得当前的行号和函数名。这是有人在论坛里提出的问题,底下一群人只是在猜测python为什么不像__file__一样提供__line__和__func__,但是却最终也没有找到解决方案。2.如果一个函数在不知道自己名字的情况下,怎么才能递归调用自己。这是我一个同事问我的,其实也是获取函数名,但是当时也是回答不出来。

但是今晚!所有的问题都有了答案。一切还要从我用python的logging模块说起,logging中的format中是有如下选项的:

代码如下:

%(name)s name of the logger (logging channel)%(levelno)s numeric logging level for the message (debug, info, warning, error, critical)%(levelname)s text logging level for the message (“debug”, “info”, “warning”, “error”, “critical”)%(pathname)s full pathname of the source file where the logging call was issued (if available)%(filename)s filename portion of pathname%(module)s module (name portion of filename)%(lineno)d source line number where the logging call was issued (if available)%(funcname)s function name%(created)f time when the logrecord was created (time.time() return value)%(asctime)s textual time when the logrecord was created%(msecs)d millisecond portion of the creation time%(relativecreated)d time in milliseconds when the logrecord was created, relative to the time the logging module was loaded (typically at application startup time)%(thread)d thread id (if available)%(threadname)s thread name (if available)%(process)d process id (if available)%(message)s the result of record.getmessage(), computed just as the record is emitted

也就是说,logging是能够获取到调用者的行号和函数名的,那会不会也可以获取到自己的行号和函数名呢?我们来看一下源码,主要部分如下:

代码如下:

def currentframe(): “””return the frame object for the caller’s stack frame.””” try: raise exception except: return sys.exc_info()[2].tb_frame.f_backdef findcaller(self): “”” find the stack frame of the caller so that we can note the source file name, line number and function name. “”” f = currentframe() #on some versions of ironpython, currentframe() returns none if #ironpython isn’t run with -x:frames. if f is not none: f = f.f_back rv = “(unknown file)”, 0, “(unknown function)” while hasattr(f, “f_code”): co = f.f_code filename = os.path.normcase(co.co_filename) if filename == _srcfile: f = f.f_back continue rv = (co.co_filename, f.f_lineno, co.co_name) break return rvdef _log(self, level, msg, args, exc_info=none, extra=none): “”” low-level logging routine which creates a logrecord and then calls all the handlers of this logger to handle the record. “”” if _srcfile: #ironpython doesn’t track python frames, so findcaller throws an #exception on some versions of ironpython. we trap it here so that #ironpython can use logging. try: fn, lno, func = self.findcaller() except valueerror: fn, lno, func = “(unknown file)”, 0, “(unknown function)” else: fn, lno, func = “(unknown file)”, 0, “(unknown function)” if exc_info: if not isinstance(exc_info, tuple): exc_info = sys.exc_info() record = self.makerecord(self.name, level, fn, lno, msg, args, exc_info, func, extra) self.handle(record)

我简单解释一下,实际上是通过在currentframe函数中抛出一个异常,然后通过向上查找的方式,找到调用的信息。其中

代码如下:

rv = (co.co_filename, f.f_lineno, co.co_name)

的三个值分别为文件名,行号,函数名。(可以去http://docs.python.org/library/sys.html来看一下代码中几个系统函数的说明)ok,如果已经看懂了源码,那获取当前位置的行号和函数名相信也非常清楚了,代码如下:

代码如下:

#!/usr/bin/python# -*- coding: utf-8 -*-”’#=============================================================================# filename: xf.py# description: 获取当前位置的行号和函数名# version: 1.0#=============================================================================”’import sysdef get_cur_info(): “””return the frame object for the caller’s stack frame.””” try: raise exception except: f = sys.exc_info()[2].tb_frame.f_back return (f.f_code.co_name, f.f_lineno)def callfunc(): print get_cur_info() if __name__ == ‘__main__’: callfunc()

输入结果是:

代码如下:

(‘callfunc’, 24)

符合预期~~哈哈,ok!现在应该不用再抱怨取不到行号和函数名了吧~

=============================================================================后来发现,其实也可以有更简单的方法,如下:

代码如下:

import sysdef get_cur_info(): print sys._getframe().f_code.co_name print sys._getframe().f_back.f_code.co_nameget_cur_info()

调用结果是:

代码如下:

get_cur_info