我可以在Python中查看lexer和parser的中间结果吗？

from ply.lex import lex
from ply.yacc import yacc

# 定义词法分析器规则
tokens = (
    'NUMBER',
    'PLUS',
    'MINUS',
)

def t_NUMBER(t):
    r'\d+'
    t.value = int(t.value)
    return t

t_PLUS = r'\+'
t_MINUS = r'-'

t_ignore = ' \t\n'

# 构建词法分析器
lexer = lex()

# 构建语法分析器
def p_expression_plus(p):
    'expression : expression PLUS expression'
    p[0] = p[1] + p[3]

def p_expression_minus(p):
    'expression : expression MINUS expression'
    p[0] = p[1] - p[3]

def p_expression_number(p):
    'expression : NUMBER'
    p[0] = p[1]

parser = yacc()

# 输入源代码
source_code = '1 + 2 - 3'

# 执行词法分析
lexer.input(source_code)
for token in lexer:
    print(token)

# 执行语法分析
result = parser.parse(source_code)
print(result)