Python Source with subprocess

I'm trying to run a command line in the terminal through a python script. The command line is as follows:

vcftools --vcf <arquivo.vcf> --extract-FORMAT-info GT --out <arquivo sem extensão>

For this I have the following lines:

import os
import subprocess
import getopt
import sys

def main(argv):
    inputfile_1 = ''
    outputfile = ''
    try:
        opts, args = getopt.getopt(
            argv, "hi:o:", ["ifile=", "ofile="])
    except getopt.GetoptError:
        print ('test.py -i <inputfile_1> -o <outputfile>')
        sys.exit(2)
    for opt, arg in opts:
        if opt == '-h':
            print ('test.py -i <inputfile_1> -o <outputfile>')
            sys.exit()
        elif opt in ("-i", "--ifile"):
            inputfile_1 = arg
        elif opt in ("-o", "--ofile"):
            outputfile = arg
    print ('O arquivo de input i: %s' % (inputfile_1))
    print ('O arquivo de output: %s' % (outputfile))

if __name__ == "__main__":
    main(sys.argv[1:])


proc = subprocess.Popen(["vcftools --vcf" + inputfile_1 + "--extract-FORMAT-info GT --out" + outputfile], stdout=subprocess.PIPE, shell=True)
(out, err) = proc.communicate()

And the error I'm getting:

guido-5:vcfx_statistics_gvcf_herc2 debortoli$ python vcftools.py -i herc2.gvcf.statistics_checkad.vcf -o test_vcf_ad

O arquivo de input i: herc2.gvcf.statistics_checkad.vcf
O arquivo de output: test_vcf_ad

Traceback (most recent call last):
      File "vcftools.py", line 30, in <module>
        proc = subprocess.Popen(["vcftools --vcf" + inputfile_1 + "--extract-FORMAT-info GT --out" + outputfile], stdout=subprocess.PIPE, shell=True)
    NameError: name 'inputfile_1' is not defined

By the way the error is in the assignment of inputfile_1 to sys.argv[1]...

Any help will be welcome.