python中使用sys模板和logging模块获取行号和函数名的方法

程序员文章站 2022-04-13 12:13:45

...

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:

复制代码代码如下:

%(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:

复制代码代码如下:

def currentframe():
"""Return the frame object for the caller's stack frame."""
try:
raise Exception
except:
return sys.exc_info()[2].tb_frame.f_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

复制代码代码如下:

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:

复制代码代码如下:

#!/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:

复制代码代码如下:

('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:

复制代码代码如下:

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:

复制代码代码如下:

get_cur_info