Python无法执行赋值操作

Question

我正在尝试创建一个以我的脚本作为输入的解释器。我写正则表达式有些问题。其中一个已定义的标记将所有字符串视为其标记。你知道吗

import ply.lex as lex
import ply.yacc as yacc

tokens = (
    'STAIRCASE',
    'STAIRCASE_END',
    'STAIR',
    'STAIR_END',
    'TAG',
    'COLON_SYM',
    'LINE_START_SYM',
    'NONE',
    'USER_DEFINED',
    'ARRAY',
    'IS',
)

assignments = {}

t_STAIRCASE                 = r'staircase'
t_TAG                       = r'\(([a-zA-Z0-9\ ])*\)'
t_COLON_SYM                 = r' :'
t_LINE_START_SYM            = r'-'
t_STAIRCASE_END             = 'EOSC'
t_ignore                    = ' \t\n'
t_STAIR                     = 'stair'
t_STAIR_END                 = 'EOS'
t_NONE                      = 'EOP'

这就是这个常规解释的问题

t_USER_DEFINED              = r'[a-zA-Z0-9]+'

代码继续

t_IS                        = 'is'

def t_error(t):
    print 'Illegal character "%s"' % t.value[0]
    t.lexer.skip(1)
lex.lex()

NONE, STAIRCASE, TAG, STAIRCASE_DESCRIPTION = range(4)
states = ['NONE', 'STAIRCASE','STAIRCASE_DESCRIPTION']
current_state = NONE

def x():
    print "Hi How you doing"

def p_staircase_def(t):
    """STAIRCASE_DEF         : STAIRCASE TAG COLON_SYM STAIRCASE_DESCRIPTION
                             """
    print t[0:]
    help(t)

def p_staircase_description(t):
    """STAIRCASE_DESCRIPTION : LINE_START_SYM DICTONARY STAIRCASE_DESCRIPTION
                             | STAIRCASE_END STAIR_DEF
                             """
    print t[0:]

def p_dictonary(t):
    """
    DICTONARY                : USER_DEFINED IS USER_DEFINED
                             """

这是我的赋值操作，实际上它创建了一个变量字典

    temp = { t[1] : t[2] }
    print assignments.update( temp )

def p_stair_def(t):
    """STAIR_DEF             : STAIR TAG COLON_SYM STAIR_DESCRIPTION
                             """
    print t[0:]

def p_stair_description(t):
    """STAIR_DESCRIPTION     : LINE_START_SYM DICTONARY STAIR_DESCRIPTION
                             | STAIR_END STAIR_DEF
                             | STAIR_END
                             """
    print t[0:]

def p_error(t):
    print 'Syntax error at "%s"' % t.value if t else 'NULL'
    global current_state
    current_state = NONE

yacc.yacc()

file_input = open("x.staircase","r")
yacc.parse(file_input.read())

这是一个示例输入，需要我的解释器“x.stairway”接受

staircase(XXXX XXX XXX):
- abc is 23183       # which need to {'abc' : '23183'}
- bcf is fda
- deh is szsC
EOSC
stair(XXXX XXX XXX):
- lkm is 35
- raa is 233
EOS
stair(XXXX XXX XXX):
- faa is zxhfb
- faa is 1
EOS

我犯了个错误

Syntax error at "staircase"
[Finished in 0.1s]

下面的代码可以工作，但输入文件不是预期的

import ply.lex as lex
import ply.yacc as yacc

tokens = (
    'STAIRCASE',
    'STAIRCASE_END',
    'STAIR',
    'STAIR_END',
    'TAG',
    'COLON_SYM',
    'LINE_START_SYM',
    'NONE',
    'USER_DEFINED',
    'ARRAY',
    'IS',
)

assignments = {}

t_STAIRCASE                 = r'staircase'
t_TAG                       = r'\(([a-zA-Z0-9\ ])*\)'
t_COLON_SYM                 = r' :'
t_LINE_START_SYM            = r'-'
t_STAIRCASE_END             = 'EOSC'
t_ignore                    = ' \t\n'
t_STAIR                     = 'stair'
t_STAIR_END                 = 'EOS'
t_NONE                      = 'EOP'

##########################################
Here is the issue with this regular exprission

It worked, If I Use this
t_USER_DEFINED              = r'a'

Instead of this
#t_USER_DEFINED              = r'[a-zA-Z0-9]+'

But, when it comes to my input file it only accept one variable called 'a'
##########################################
Code continues

t_IS                        = 'is'

def t_error(t):
    print 'Illegal character "%s"' % t.value[0]
    t.lexer.skip(1)
lex.lex()

NONE, STAIRCASE, TAG, STAIRCASE_DESCRIPTION = range(4)
states = ['NONE', 'STAIRCASE','STAIRCASE_DESCRIPTION']
current_state = NONE

def x():
    print "Hi How you doing"

def p_staircase_def(t):
    """STAIRCASE_DEF         : STAIRCASE TAG COLON_SYM STAIRCASE_DESCRIPTION
                             """
    print t[0:]
    help(t)

def p_staircase_description(t):
    """STAIRCASE_DESCRIPTION : LINE_START_SYM DICTONARY STAIRCASE_DESCRIPTION
                             | STAIRCASE_END STAIR_DEF
                             """
    print t[0:]

def p_dictonary(t):
    """
    DICTONARY                : USER_DEFINED IS USER_DEFINED
                             """

HERE is my assignment operation, actually it create a dictionary of variables

    temp = { t[1] : t[2] }
    print assignments.update( temp )

def p_stair_def(t):
    """STAIR_DEF             : STAIR TAG COLON_SYM STAIR_DESCRIPTION
                             """
    print t[0:]

def p_stair_description(t):
    """STAIR_DESCRIPTION     : LINE_START_SYM DICTONARY STAIR_DESCRIPTION
                             | STAIR_END STAIR_DEF
                             | STAIR_END
                             """
    print t[0:]

def p_error(t):
    print 'Syntax error at "%s"' % t.value if t else 'NULL'
    global current_state
    current_state = NONE

yacc.yacc()

file_input = open("x.staircase","r")
yacc.parse(file_input.read())

下面给出的是一个示例输入（“x.stairway”）工程。但正如您所看到的，所有用户定义的

staircase(XXXX XXX XXX):
- a is a       # which need to {'abc' : '23183'}
- a is a
- a is a
EOSC
stair(XXXX XXX XXX):
- a is a
- a is a
EOS
stair(XXXX XXX XXX):
- a is a
- a is a 1
EOS

Answer 1

请（重新）阅读Ply的lexer如何识别Ply manual中的标记的描述。请特别注意排序规则；由于模式变量从最长到最短排序，因此在任何关键字模式（如staircase）之前都会尝试t_USER_DEFINED模式，因此不会识别任何关键字。（这就是为什么将t_USER_DEFINED缩短为单个字符会改变词汇行为。）

有一个很好的线索表明，这是问题所在，而不是赋值结果：错误消息是在标记staircase处触发的，早在遇到赋值之前。通过在p_error函数中打印t.type和t.value，您将获得另一条线索。（当然，也可以在尝试解析任何内容之前测试tokeniser）

如果您通读到我链接的Ply手册的最后一节，您会发现一个关于如何处理关键字标记的建议，使用scanner函数和关键字辅助字典。我强烈建议你用它作为你的榜样。你知道吗

另请注意，要求冒号前面加空格字符：

t_COLON_SYM                 = r' :'

但是您的示例输入在冒号之前没有空格。你知道吗