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Date: Wed, 21 Aug 2013 11:42:11 -0500
Subject: Re: Raw_input with readline in a daemon thread makes terminal text disappear
From: "David M. Welch" <david.m.welch@gmail.com>
To: <python-list@python.org>
Thread-Topic: Raw_input with readline in a daemon thread makes terminal text disappear
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Hi all, 

This is an old thread, but I'm having the same behavior in my terminal when
I run some code but kill the process in the terminal (Ctrl-C).  The code has
two prime suspects (from a simple google search):
1. Creates ssh port forward via the subprocess module
(http://unix.stackexchange.com/questions/4740/screen-remote-login-failure-an
d-disappearing-text)
2. Using the getpass module (raw_input?)
Calling "$ reset" brings back the disappearing text, so I'm just wondering
if this issue has been addressed and if so, what should I be doing that I'm
not.

Thank you,
Dave W.
Response to post: 
http://mail.python.org/pipermail/python-list/2009-October/554784.html
I'm getting input for a program while it's running by using raw_input in a
loop in separate thread. This works except for the inconvenience of not
having 
a command history or the use of backspace etc.

That can be solved by loading the readline module; however, it results in a
loss of visible access to the terminal when the program ends: nothing is
echoed to the screen and the history is invisible (although it is there -
hitting return executes whatever should be there normally). The only way to
get it back is to close the terminal and open a new one.

Here is minimal code that reproduces the problem (python 2.5 on Linux):

from threading import Thread
import readline

get_input = Thread(target=raw_input)
get_input.setDaemon(True)
get_input.start()

If the thread is not set to daemon mode, there is no such problem (don't
know 
why this makes a difference), but in the real program, it needs to be a
daemon 
or it hangs the exit waiting for more input.

Any suggestions appreciated.

Thanks,

John



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<html><head></head><body style=3D"word-wrap: break-word; -webkit-nbsp-mode: s=
pace; -webkit-line-break: after-white-space; color: rgb(0, 0, 0); font-size:=
 14px; font-family: Calibri, sans-serif; "><div style=3D"font-size: 14px; font=
-family: Calibri, sans-serif; ">Hi all,&nbsp;</div><div style=3D"font-size: 14=
px; font-family: Calibri, sans-serif; "><br></div><font face=3D"Calibri,sans-s=
erif" style=3D"font-size: 14px; ">This is an old thread, but I'm having the sa=
me behavior in my terminal when I run some code but kill the process in the =
terminal (Ctrl-C). &nbsp;The code has two prime suspects (from a simple goog=
le search):</font><ol style=3D"font-size: 14px; font-family: Calibri, sans-ser=
if; "><li>Creates ssh port forward via the subprocess module (<a href=3D"http:=
//unix.stackexchange.com/questions/4740/screen-remote-login-failure-and-disa=
ppearing-text">http://unix.stackexchange.com/questions/4740/screen-remote-lo=
gin-failure-and-disappearing-text</a>)</li><li>Using the getpass module (raw=
_input?) &nbsp;</li></ol><div style=3D"font-size: 14px; font-family: Calibri, =
sans-serif; ">Calling "$ reset" brings back the disappearing text, so I'm ju=
st wondering if this issue has been addressed and if so, what should I be do=
ing that I'm not.</div><div style=3D"font-size: 14px; font-family: Calibri, sa=
ns-serif; "><br></div><div style=3D"font-size: 14px; font-family: Calibri, san=
s-serif; ">Thank you,</div><div style=3D"font-size: 14px; font-family: Calibri=
, sans-serif; ">Dave W.</div><div><pre><font face=3D"Calibri" style=3D"font-size=
: 12px;">Response to post: <a href=3D"http://mail.python.org/pipermail/python-=
list/2009-October/554784.html">http://mail.python.org/pipermail/python-list/=
2009-October/554784.html</a></font></pre><pre><font face=3D"Consolas" style=3D"f=
ont-size: 12px;">I'm getting input for a program while it's running by using=
 raw_input in a 
loop in separate thread. This works except for the inconvenience of not hav=
ing 
a command history or the use of backspace etc. 

That can be solved by loading the readline module; however, it results in a=
 
loss of visible access to the terminal when the program ends: nothing is 
echoed to the screen and the history is invisible (although it is there - 
hitting return executes whatever should be there normally). The only way to=
 
get it back is to close the terminal and open a new one.

Here is minimal code that reproduces the problem (python 2.5 on Linux): 

from threading import Thread
import readline

get_input =3D Thread(target=3Draw_input)
get_input.setDaemon(True)
get_input.start()

If the thread is not set to daemon mode, there is no such problem (don't kn=
ow 
why this makes a difference), but in the real program, it needs to be a dae=
mon 
or it hangs the exit waiting for more input.

Any suggestions appreciated.

Thanks,

John</font></pre></div></body></html>

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