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:

%(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:

def currentframe():
    """return the frame object for the caller's stack frame."""
    try:
        raise exception
    except:
        return sys.exc_info()[2].tb_frame.f_back
def 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 rv
def _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

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:

#!/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 sys
def 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:

('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:

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

调用结果是:

get_cur_info
<module>