I have files with naming convention

st009_out.abc1.dat
st009_out.abc2.dat
st009_out.abc3.dat 
..................
..................

I am writing Python code where I want to use data from the file to perform a math function and need to extract the second column from the file. I have tried it this way:

for k in range(1,10):
    file1=open('st009_out.abc'+str(k)+'.dat','r')
    ...........
    os.system("awk '{print $2}' st009_out.abc${k}.pmf > raj.dat")

but this is not working as it is not taking the value of k in the shell command.

How do I progress?