RPLY program that is giving a weird error. - Has test data at the bottom, Just run the file to test,

gistfile1.txt

PS D:\Compiler\BoatCPU\ASM> ..\..\..\python39\python.exe .\main.py
Traceback (most recent call last):
  File "D:\Compiler\BoatCPU\ASM\main.py", line 84, in <module>
    print(parser.parse(lexer.lex(q)))
  File "D:\python39\lib\site-packages\rply\parser.py", line 22, in parse
    current_state = self._reduce_production(
  File "D:\python39\lib\site-packages\rply\parser.py", line 80, in _reduce_production
    value = p.func(targ)
  File "D:\Compiler\BoatCPU\ASM\main.py", line 26, in expressions_expressions_expression
    return t.append(p[1])
AttributeError: 'NoneType' object has no attribute 'append'
PS D:\Compiler\BoatCPU\ASM>

main.py

from rply import LexerGenerator, ParserGenerator

lg = LexerGenerator()
lg.ignore(r'\s+')
lg.ignore(r'\n+')
lg.add('REGISTER',r'[ABCDEFGHIJKLMNO]')
lg.add('ASSEMBLER_DIRECTIVE',r'org|def')
lg.add('OPCODE',r'nop|loadimm|loadram|loadregister|loadpc|loadstatus|loadstack|storeram|storeregister|storestack|push|pop|or|xor|and|add|sub|not|compare|shiftleft|shiftright|loadimm8|loadram8|loadregister8|loadstatus8|storeram8|storeregister8|push8|pop8|or8|xor8|and8|add8|sub8|not8|compare8|shiftleft8|shiftright8|jump|jumproffset|jumproffset8|jumpoffset|jumprelativeregister|jumprelativeregister8|jumpregister|jumpregisteroffset|branche|branchg|branchl|brancho|intrrupt|intrruptvector|returnint|disableint|storestatus|enableint')
lg.add('NAME',r'[a-zA-Z] [a-zA-Z0-9."]*')
lg.add('NUMBER',r"\b(0x[0-9a-fA-F]+|[0-9]+)\b")

lexer = lg.build()


pg = ParserGenerator(
    # A list of all token names, accepted by the parser.
    ['NUMBER', 'REGISTER', 'OPCODE',
     'NAME'
    ]
)


@pg.production('expressions : expressions expression')
def expressions_expressions_expression(p):
    t = p[0]
    return t.append(p[1])

@pg.production('expressions : ')
def expressions_expressions_expression(p):
    return []


@pg.production('expression : OPCODE REGISTER')
def expression_singleReg(p):
    # p is a list of the pieces matched by the right hand side of the
    # rule

    return p


@pg.production('expression : OPCODE REGISTER REGISTER')
def expression_doubleReg(p):
    # p is a list of the pieces matched by the right hand side of the
    # rule

    return p
    
@pg.production('expression : OPCODE REGISTER REGISTER REGISTER')
def expression_tripleReg(p):
    # p is a list of the pieces matched by the right hand side of the
    # rule

    return p
    
    
@pg.production('expression : OPCODE REGISTER NUMBER')
def expression_regNum(p):
    # p is a list of the pieces matched by the right hand side of the
    # rule

    return p
    
@pg.production('expression : OPCODE REGISTER NAME')
def expression_regName(p):
    # p is a list of the pieces matched by the right hand side of the
    # rule

    return p
    
@pg.error
def error_handler(token):
    raise ValueError("Ran into a %s where it wasn't expected" % token.gettokentype())
    
parser = pg.build()




q = """loadimm A 100
loadimm B 100
add A B C
storeram C 2000"""

print(parser.parse(lexer.lex(q)))