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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 -*-
'''
#=============================================================================
#  Author:          dantezhu - http://www.vimer.cn
#  Email:           zny2008@gmail.com
#  FileName:        xf.py
#  Description:     获取当前位置的行号和函数名
#  Version:         1.0
#  LastChange:      2010-12-17 01:19:19
#  History:         
#=============================================================================
'''
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>

 

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评论

  1. Jeffrey4l

    Jeffrey4l on #

    好巧妙的方法~记下,以后应该用的着。

    Reply

  2. mmplayer

    mmplayer on #

    不错 马克

    Reply

  3. iCyOMiK

    iCyOMiK on #

    好东西自然要回复,回头再看。

    Reply

  4. GlacJAY

    GlacJAY on #

    Google 了一下,用 inspect 模块的 currentframe 和 getframeinfo 两个函数就可以得到行数和函数名了,不需要抛异常什么的。

    Reply

    1. Dante

      Dante on #

      嗯,后来确实发现还有别的写法:
      def get_cur_info():
      print sys._getframe().f_code.co_name
      print sys._getframe().f_back.f_code.co_name

      Reply

  5. Jean Combs

    Jean Combs on #

    好巧妙的方法~记下,以后应该用的着。

    Reply

  6. BaiDu

    BaiDu on #

    When I initially commented I clicked the "Notify me when new comments are added" checkbox and now each time a comment is added I get four e-mails with the same comment. Is there any way you can remove people from that service? Cheers!

    Reply

  7. caimaoy

    caimaoy on #

    为什么我的python没有这个函数啊?

    Reply

    1. 朱念洋

      朱念洋 on #

      应该都有吧。。是不是包没导入?

      Reply

  8. eezz

    eezz on #

    最后的方法很实用!!

    Reply

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