import re
regex = r"\\{2,}"
test_str = r"%Software\\Policies\\\\Microsoft\\Windows\\Safer\\CodeIdentifiers\\0\\Hashes\\"
subst = r"\\"
result = re.sub(regex, subst, test_str,0)
if result:
print (result)# your code goes here
aW1wb3J0IHJlCnJlZ2V4ID0gciJcXHsyLH0iCnRlc3Rfc3RyID0gciIlU29mdHdhcmVcXFBvbGljaWVzXFxcXE1pY3Jvc29mdFxcV2luZG93c1xcU2FmZXJcXENvZGVJZGVudGlmaWVyc1xcMFxcSGFzaGVzXFwiCgkKIApzdWJzdCA9IHIiXFwiCnJlc3VsdCA9IHJlLnN1YihyZWdleCwgc3Vic3QsIHRlc3Rfc3RyLDApCiAKaWYgcmVzdWx0OgogICAgcHJpbnQgKHJlc3VsdCkjIHlvdXIgY29kZSBnb2VzIGhlcmU=