Calling Python from Tcl

wombat.py

#!/usr/bin/python

import itertools as it

class pi_computing_device(object):
    def __init__(self, iterations):
        self.n = iterations

    def compute_pi(self):
        coefficients = it.cycle((1, -1))
        divisors = it.islice(it.count(1), 0, self.n, 2)
        return 4*sum(c * 1.0/d for c, d in it.izip(coefficients, divisors))

wombat.tcl

# Open a file stream to an interactive Python session
set pystream [open "|/usr/bin/python -i wombat.py" r+]
fconfigure $pystream -blocking 0

# Ask Python to calculate Pi
puts $pystream "w = pi_computing_device(1000)"
puts $pystream "print w.compute_pi()"
flush $pystream

# Spin until we get a response from Python
# Probably better to use "filevent"
while {1} {
    set L [gets $pystream foo]

    # Print it to the screen in Tcl
    if {$foo != ""} {
        puts "Pi is approximately equal to $foo"
        break
    }
}

# Close the stream to shut down Python
close $pystream

Hi , this is already an old post I guess .
But I am stuked , and hope I can get some help here.
I am running Phyton fron TCL .
The difference between this case and mine is that I must work on same session (so no close session is allowed ) .
Now the issue is , that Python keeps on getting same commands over and over from TCL. I am sending each time different commands .
My phyton opens an ssh stream .
First line is puts $pystream "ls -l" .
As expected getting the correct output .
Next sending put $pystream "some other command" . And still getting same response as the previous . I am using the flush, as mentioned .