Start a subprocess, wait for it to complete and then retrieve data in Python

I'm struggling to get some python script to start a subprocess, wait until it completes and then retrieve the required data. I'm quite new to Python.

The command I wish to run as a subprocess is

    ./bin.testing/Eva -t --suite="temp0"

Running that command by hand in the Linux terminal produces:

    in terminal mode
    Evaluation error = 16.7934

I want to run the command as a python sub-process, and receive the output back. However, everything I try seems to skip the second line (ultimately, it's the second line that I want.) At the moment, I have this:

    def job(self,fen_file):
        from subprocess import Popen, PIPE
        from sys import exit

        try:
            eva=Popen('{0}/Eva -t --suite"{0}"'.format(self.exedir,fen_file),shell=True,stdout=PIPE,stderr=PIPE)            
            stdout,stderr=eva.communicate()
        except:
            print ('Error running test suite '+fen_file)
            exit("Stopping")

        print(stdout) 
        .
        .
        .
        return 0

All this seems to produce is

    in terminal mode

    0

with the important line missing. The print statement is just so I can see what I am getting back from the sub-process -- the intention is that it will be replaced with code that processes the number from the second line and returns the output (here I'm just returning 0 just so I can get this particular bit to work first. The caller of this function prints the result, which is why there is a zero at the end of the output.) exedir is just the directory of the executable for the sub-process, and fen-file is just an ascii file that the sub-process needs. I have tried removing the 'in terminal mode' from the source code of the sub-process and re compiling it, but that doesn't work -- it still doesn't return the important second line.

Thanks in advance; I expect what I am doing wrong is really very simple.

Edit: I ought to add that the subprocess Eva can take a second or two to complete.