Enter interactive mode in piped python scripts [duplicate]

Question

This question already has answers here:

Embed (create) an interactive Python shell inside a Python program (5 answers)

Closed 9 years ago.

I am trying to pipe 2 python scripts using the shell pipe operator "|", like this:

python s1.py | python s2.py

In the simpliest case, s1.py and s2.py do nothing but print some strings:

in s1.py:

print 'from s1.'

in s2.py:

import sys
for line in sys.stdin.readlines():
 print 'from s2: '+line

I would like to enter interactive mode after executing s2.py. I have tried to put the -i flag in front of s1.py, s2.py and both. But none of them give the desired result. Putting import pdb;pdb.set_trace() at the end of s2.py doesn't help either.

Could anyone give some clue? Btw, my python version is 2.5.2

Answer 1

You'll need to reset stdin to come from the terminal, rather than the pipe. That is, before asking for input from the user (and assuming you're on a Unix-y environment) invoke sys.stdin = open("/dev/tty"). For example:

import sys
for line in sys.stdin.readlines():
 print 'from s2: ' + line
sys.stdin = open("/dev/tty")
raw_input()

• Jason: Thanks for answering so quickly. I think a combination of your suggestion and this one solves my problem. I tried to redirect the sys.stdin and also used code module and now it seems to be working.
• Holger Brandl: @Jason could you post your final solution? I'd like to do the same (get a shell where I can read the piped-in data from stdin) but somehow don't manage to combine both solutions.
• Jason: @HolgerBrandl sorry for late reply. I've added my solution, basically I'm checking if a script is receiving the inputs from atty or not, and if it is not re-directing to another script, it enters an interactive session, where the variables etc. are retained following this post. Hope it helps.

Answer 2

To give a more clear answer based on suggestions by jme and the discussion:

As a minimal working example, in s1.py:

print "from s1.py"

In s2.py:

import sys
import readline # optional, will allow Up/Down/History in the console
import code
red_out=not sys.stdout.isatty() # check if re-directing out
red_in=not sys.stdin.isatty() # chech if re-directed in
#------Print out the re-directed in messages------
if red_in:
 for line in sys.stdin.readlines():
 print line.strip()
#--- Enter interactive session if not re-directing out---
if not red_out:
 sys.stdin = open("/dev/tty")
 shell=code.InteractiveConsole(vars)
 shell.interact()

And finally to launch it, python s1.py | python s2.py