在IPython中捕获SIGTSTP

Question

为SIGTSTP注册信号处理程序在普通的Python解释器中工作。

(py3)$ python
Python 3.4.3 |Continuum Analytics, Inc.| (default, Mar  6 2015, 12:07:41) 
[GCC 4.2.1 (Apple Inc. build 5577)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import signal
>>> def handler(x, frame):
...     print("CAUGHT", x)
... 
>>> signal.signal(signal.SIGTSTP, handler)
0

现在我按Ctrl + Z几次，它按预期工作。

>>> CAUGHT 18
CAUGHT 18
CAUGHT 18

但是，在IPython中，它不起作用。调用新的处理程序，但似乎也调用了原始处理程序，并且IPython已停止。

IPython 3.2.0 -- An enhanced Interactive Python.
Anaconda is brought to you by Continuum Analytics.
Please check out: http://continuum.io/thanks and https://anaconda.org
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: def handler(x, frame):
    print("CAUGHT", x)
   ...:     

In [2]: import signal

In [3]: signal.signal(signal.SIGTSTP, handler)
Out[3]: 0

现在我点击Ctrl + Z：

In [4]: CAUGHT 18

[2]+  Stopped                 ipython

顺便说一下，我没有看到Ctrl + C的问题：

In [5]: signal.signal(signal.SIGINT, handler)
Out[5]: <function signal.default_int_handler>

In [6]: CAUGHT 2

IPython使用SIGTSTP做什么？神秘的是，我在IPython 3.2代码库中找不到任何字符串'SIGTSTP'。