You may take inspiration from this Python script that I wrote last year. This just splits multi-allelic sites in the same way as bcftools norm -m-any. Take a look at what it does and then edit it to suit your own needs.

Execute it as

python Split.py [Input VCF] [Output VCF]

.

#Name:          Kevin Blighe
#Email:         NA
#Date:          20th July 2017
#Function(s):   Splits multiallelels

import sys
import os

#Check the number of command line arguments
if not len(sys.argv)==3:
    print "\nError:\tincorrect number of command-line arguments"
    print "Syntax:\tSplit.py [Input VCF] [Output VCF]\n"
    sys.exit()

if sys.argv[1]==sys.argv[2]:
    #boolOverwrite = raw_input("\nInput file is the same as the output file - overwrite input file (sim/nao)?\n")
    print "Error:\tInput file is the same as the output file - choose a different output file\n"
    sys.exit()

#File input
fileInput = open(sys.argv[1], "r")

#File output for split multi-alleles
fileOutput = open(sys.argv[2], "w")

#Loop through each line in the input file, and split multiallelic sites
print ("Splitting multi-allelic sites...")
for strLine in fileInput:
    #Strip the endline character from each input line
    strLine = strLine.rstrip("\n")

    #The '#' character in VCF format indicates that the line is a header. Ignore these and just output to the new file
    if strLine.startswith("#"):
        fileOutput.write(strLine + "\n")
    else:
        #Split the tab-delimited line into an array
        strArray = [splits for splits in strLine.split("\t") if splits is not ""]

        #Check first if it's multiallelic
        #Multi-allelic variants will have 2 calls in the VAR field, separated by a comma (',')
        if "," in strArray[4]:
            strVars = [splits for splits in strArray[4].split(",") if splits is not ""]
            iNumMultialleles = len(strVars)

            for i in range(0, (iNumMultialleles)):
                strArray[4] = strVars[i]
                fileOutputTemp.write("\t".join(strArray) + "\n")
        else:
            fileOutput.write("\t".join(strArray) + "\n")
print ("Done.")

#Close the files
fileInput.close()
fileOutput.close()