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 levelfor the message (DEBUG, INFO,
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WARNING, ERROR, CRITICAL)
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%(levelname)s Text logging levelfor the message ("DEBUG","INFO",
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"WARNING","ERROR","CRITICAL")
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%(pathname)s Full pathname of the sourcefile 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 Timein 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 ThreadID (if available)
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%(threadName)s Thread name (if available)
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%(process)d ProcessID (if available)
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%(message)s The result of record.getMessage(), computed just as
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the recordis 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:
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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 fis 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)
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
1
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:
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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: [email protected]
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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:
12
#=============================================================================
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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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23
def callfunc():
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print get_cur_info()
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26
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if __name__== '__main__':
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callfunc()
输入结果是:
1
('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:
1
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).
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