C语言有__LINE__来表示源代码的当前行号，经常在记录日志时使用。Python如何获取源代码的当前行号？

The C Language has the __LINE__ macro, which is wildly used in logging, presenting the current line of the source file. And how to get the current line of a Python source file?

exception输出的函数调用栈就是个典型的应用：

A typical example is the output of function call stack when an exception:

python代码

File

"D:\workspace\Python\src\lang\lineno.py", line

19,

in

>

afunc

(

)

File

"D:\workspace\Python\src\lang\lineno.py", line

15,

in afunc

errmsg =

1/

0

ZeroDivisionError: integer division

or modulo by zero

那么我们就从错误栈的输出入手，traceback模块中：

Now that, Let's begin with the output of an exception call stack, in the traceback module:

python代码

def print_stack

(f=

None, limit=

None,

file=

None

):

"""Print a stack trace from its invocation point.

The optional 'f' argument can be used to specify an alternate

stack frame at which to start. The optional 'limit' and 'file'

arguments have the same meaning as for print_exception().

"""

if f

is

None:

try:

raise

ZeroDivisionError

except

ZeroDivisionError:

f =

sys.

exc_info

(

)

[

2

].

tb_frame.

f_back

print_list

(extract_stack

(f, limit

),

file

)

def print_list

(extracted_list,

file=

None

):

"""Print the list of tuples as returned by extract_tb() or

extract_stack() as a formatted stack trace to the given file."""

if

file

is

None:

file =

sys.

stderr

for filename, lineno, name, line

in extracted_list:

_print

(

file,

'  File "%s", line %d, in %s'

%

(filename,lineno,name

)

)

if line:

_print

(

file,

'    %s'

% line.

strip

(

)

)

traceback模块构造一个ZeroDivisionError，并通过sys模块的exc_info()来获取运行时上下文。我们看到，所有的秘密都在tb_frame中，这是函数调用栈中的一个帧。

traceback constructs an ZeroDivisionError, and then call the exc_info() of the sys module to get runtime context. There, all the secrets hide in the tb_frame, this is a frame of the function call stack.

对，就是这么简单！只要我们能找到调用栈frame对象即可获取到行号！因此，我们可以用同样的方法来达到目的，我们自定义一个lineno函数：

Yes, It's so easy! If only a frame object we get, we can get the line number! So we can have a similar implemetation to get what we want, defining a function named lineno:

python代码

import

sys

def lineno

(

):

frame =

None

try:

raise

ZeroDivisionError

except

ZeroDivisionError:

frame =

sys.

exc_info

(

)

[

2

].

tb_frame.

f_back

return frame.

f_lineno

def afunc

(

):

# if error

print

"I have a problem! And here is at Line: %s"

%lineno

(

)

是否有更方便的方法获取到frame对象？当然有！

Is there any other way, perhaps more convinient, to get a frame object? Of course YES!

python代码

def afunc

(

):

# if error

print

"I have a proble! And here is at Line: %s"

%

sys._getframe

(

).

f_lineno

类似地，通过frame对象，我们还可以获取到当前文件、当前函数等信息，就像C语音的__FILE__与__FUNCTION__一样。其实现方式，留给你们自己去发现。

Thanks to the frame object, similarly, we can also get current file and current function name, just like the __FILE__ and __FUNCTION__ macros in C. Debug the frame object, you will get the solutions.

http://blog.csdn.net/qinbaby/article/details/23201811