I've looked at this and it wasn't much help.
I have a Ruby program that puts a question to the cmd line and I would like to write a Python program that can return an answer. Does anyone know of any links or in general how I might go about doing this?
Thanks for your help.
EDIT
Thanks to the guys that mentioned piping. I haven't used it too much and was glad it was brought up since it forced me too look in to it more.
p = subprocess.Popen(['ruby', 'ruby_program.rb'], stdin=subprocess.PIPE,
stdout=subprocess.PIPE)
ruby_question = p.stdout.readline()
answer = calculate_answer(ruby_question)
p.stdin.write(answer)
print p.communicate()[0] # prints further info ruby may show.
The last 2 lines could be made into one:
print p.communicate(answer)[0]
If you're on unix / linux you can use piping:
question.rb | answer.py
Then the output of question.rb becomes the input of answer.py
I've not tried it recently, but I have a feeling the same syntax might work on Windows as well.
Pexpect
http://www.noah.org/wiki/Pexpect
Pexpect is a pure Python expect-like module. Pexpect makes Python a better tool for controlling other applications.
Pexpect is a pure Python module for spawning child applications; controlling them; and responding to expected patterns in their output. Pexpect works like Don Libes' Expect. Pexpect allows your script to spawn a child application and control it as if a human were typing commands.
First of all check this out: [Unix piping][1]
It works on windows or unix but it's slighly dufferent, first the programs:
question.rb:
puts "This is the question"
answer.rb:
question = gets
#calculate answer
puts "This is the answer"
Then the command line:
In unix:
question.rb | answer.rb
In windows:
ruby question.rb | ruby answer.rb
Output:
This is the question
This is the answer
| character, then the data flows one way. But you can set up a program to use both input and output pipes -- in fact, that's exactly how your Python answer works under the hood. You don't need Python for this; the Unix shell has been able to do it since the 70s.| character. So it doesn't answer the question.There are two ways (off the top of my head) to do this. The simplest if you're in a Unix environment is to use piping. Simple example:
cat .profile .shrc | more
This will send the output of the first command (cat .profile .shrc) to the more command using the pipe character |.
The second way is to call one program from the other in your source code. I'm don't know how Ruby handles this, but in Python you can run a program and get it's output by using the popen function. See this example chapter from Learning Python, then Ctrl-F for "popen" for some example code.
