http://www.vimer.cn/2010/12/%E5%9C%A8python%E4%B8%AD%E8%8E%B7%E5%8F%96%E5%BD%93%E5%89%8D%E4%BD%8D%E7%BD%AE%E6%89%80%E5%9C%A8%E7%9A%84%E8%A1%8C%E5%8F%B7%E5%92%8C%E5%87%BD%E6%95%B0%E5%90%8D.html
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:
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%(name)s Name of the logger (logging channel)
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%(levelno)s Numeric logging level for the message (DEBUG, INFO,
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WARNING, ERROR, CRITICAL)
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%(levelname)s Text logging level for the message ("DEBUG", "INFO",
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"WARNING", "ERROR", "CRITICAL")
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%(pathname)s Full pathname of the source file where the logging
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call was issued (if available)
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%(filename)s Filename portion of pathname
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%(module)s Module (name portion of filename)
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%(lineno)d Source line number where the logging call was issued
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(if available)
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%(funcName)s Function name
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%(created)f Time when the LogRecord was created (time.time()
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return value)
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%(asctime)s Textual time when the LogRecord was created
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%(msecs)d Millisecond portion of the creation time
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%(relativeCreated)d Time in milliseconds when the LogRecord was created,
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relative to the time the logging module was loaded
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(typically at application startup time)
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%(thread)d Thread ID (if available)
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%(threadName)s Thread name (if available)
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%(process)d Process ID (if available)
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%(message)s The result of record.getMessage(), computed just as
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the record is emitted
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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:
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def currentframe():
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"""Return the frame object for the caller's stack frame."""
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try:
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raise Exception
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except:
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return sys.exc_info()[2].tb_frame.f_back
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def findCaller(self):
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"""
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Find the stack frame of the caller so that we can note the source
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file name, line number and function name.
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"""
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f = currentframe()
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#On some versions of IronPython, currentframe() returns None if
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#IronPython isn't run with -X:Frames.
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if f is not None:
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f = f.f_back
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rv = "(unknown file)", 0, "(unknown function)"
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while hasattr(f, "f_code"):
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co = f.f_code
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filename = os.path.normcase(co.co_filename)
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if filename == _srcfile:
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f = f.f_back
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continue
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rv = (co.co_filename, f.f_lineno, co.co_name)
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break
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return rv
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def _log(self, level, msg, args, exc_info=None, extra=None):
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"""
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Low-level logging routine which creates a LogRecord and then calls
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all the handlers of this logger to handle the record.
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"""
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if _srcfile:
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#IronPython doesn't track Python frames, so findCaller throws an
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#exception on some versions of IronPython. We trap it here so that
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#IronPython can use logging.
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try:
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fn, lno, func = self.findCaller()
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except ValueError:
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fn, lno, func = "(unknown file)", 0, "(unknown function)"
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else:
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fn, lno, func = "(unknown file)", 0, "(unknown function)"
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if exc_info:
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if not isinstance(exc_info, tuple):
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exc_info = sys.exc_info()
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record = self.makeRecord(self.name, level, fn, lno, msg, args, exc_info, func, extra)
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self.handle(record)
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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
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rv = (co.co_filename, f.f_lineno, co.co_name)
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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:
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#!/usr/bin/python |
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# -*- coding: utf-8 -*- |
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''' |
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#============================================================================= |
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# Author: dantezhu - http://www.vimer.cn |
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# Email: zny2008@gmail.com |
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# FileName: xf.py |
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# Description: 获取当前位置的行号和函数名 |
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# Version: 1.0 |
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# LastChange: 2010-12-17 01:19:19 |
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# History: |
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#============================================================================= |
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''' |
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import sys
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def get_cur_info():
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"""Return the frame object for the caller's stack frame."""
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try:
|
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raise Exception
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except:
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f = sys.exc_info()[2].tb_frame.f_back
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return (f.f_code.co_name, f.f_lineno)
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|
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def callfunc():
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print get_cur_info()
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if __name__ == '__main__':
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callfunc()
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输入结果是:
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('callfunc', 24)
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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:
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import sys
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def get_cur_info():
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print sys._getframe().f_code.co_name
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print sys._getframe().f_back.f_code.co_name
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get_cur_info() |
================================================================================
另外,利用python的 inspect 模块中的getframeinfo也可以得到.
- inspect.getframeinfo( frame [, context ])
-
Get information about a frame or traceback object. A 5-tuple is returned, the last five elements of the frame’s frame record.
Changed in version 2.6: Returns a named tuple Traceback(filename, lineno, function,code_context, index).