# 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