from pyparsing import quotedString from datetime import datetime nw = datetime.utcnow() nowstring = '"%s"' % (nw.strftime("%d %b %Y %X")[:-3] + " UTC") print(nowstring) quoted_time = quotedString() quoted_time.setParseAction(lambda: nowstring) version_time = "__versionTime__ = " + quoted_time with open("pyparsing.py", encoding="utf-8") as oldpp: orig_code = oldpp.read() new_code = version_time.transformString(orig_code) with open("pyparsing.py", "w", encoding="utf-8") as newpp: newpp.write(new_code)