Example code:

from pykat import finesse
from pykat.commands import *
kat = finesse.kat()
kat.verbose = False

code = """
l laser1 1.0 0 n1 
s s1 0 n1 n2 
pd pow_t n2
const rx 1
#m m1 $rx 0 0 n2 n3

xaxis laser1 P lin 0 1 10 
yaxis abs                 
"""

code2 = "m m1 $rx 0 0 n2 n3"

kat.parseCommands(code)
kat.parseCommands(code2)

out1 = kat.run()