import re
text = '52A, XYZ Street, ABC District, 2, M, Brown'
p = r'^(.*?)(,?\s*\b\d+\b)'
text = re.sub(p, lambda x: "{}{}".format(x.group(1).replace(',', ''), x.group(2)), text)
print(text)
aW1wb3J0IHJlCnRleHQgPSAnNTJBLCBYWVogU3RyZWV0LCBBQkMgRGlzdHJpY3QsIDIsIE0sIEJyb3duJwpwID0gcideKC4qPykoLD9ccypcYlxkK1xiKScKdGV4dCA9IHJlLnN1YihwLCBsYW1iZGEgeDogInt9e30iLmZvcm1hdCh4Lmdyb3VwKDEpLnJlcGxhY2UoJywnLCAnJyksIHguZ3JvdXAoMikpLCB0ZXh0KQpwcmludCh0ZXh0KQ==