from pyparsing import delimitedList, Literal
strs = Literal("x+42") | Literal("100500") | Literal("x++")
f = delimitedList(strs, "+")
print(f.parseString("x+42+x+++100500"))
ZnJvbSBweXBhcnNpbmcgaW1wb3J0IGRlbGltaXRlZExpc3QsIExpdGVyYWwKCnN0cnMgPSBMaXRlcmFsKCJ4KzQyIikgfCBMaXRlcmFsKCIxMDA1MDAiKSB8IExpdGVyYWwoIngrKyIpCgpmID0gZGVsaW1pdGVkTGlzdChzdHJzLCAiKyIpCnByaW50KGYucGFyc2VTdHJpbmcoIngrNDIreCsrKzEwMDUwMCIpKQ==