问题描述

我正在尝试创建一个以我的脚本作为输入的解释器。我在编写正则表达式时遇到了一些问题。定义的标记之一是将所有字符串视为标记。

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'

这是这种常规表达的问题

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())

这是我的解释器“x.staircase”需要接受的示例输入

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

我得到的错误

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

以下代码有效，但输入文件与预期不符。

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 input("x.staircase") 作品。但是正如您所看到的，所有 USER_DEFINED 始终是

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

标签： pythonply

请（重新）阅读Ply 手册中关于 Ply 词法分析器如何识别标记的描述。特别注意订购规则；由于模式变量从最长到最短排序，因此t_USER_DEFINED在任何关键字模式（例如staircase）之前尝试该模式，因此不会识别任何关键字。（这就是缩短t_USER_DEFINED为单个字符会改变词汇行为的原因。）

有一个很好的线索表明这是问题而不是分配产生：在staircase遇到分配之前很久就在 token 处触发了错误消息。t.type通过打印以及t.value在您的p_error函数中，您会得到另一个线索。（或者，当然，在尝试解析任何内容之前测试标记器。）

如果您通读我链接的 Ply 手册部分的末尾，您会发现有关如何使用扫描仪功能和关键字辅助字典处理关键字标记的建议。我强烈建议您使用它作为您的模型。

另请注意，您需要冒号前面有空格字符：

t_COLON_SYM                 = r' :'

但是您的示例输入在冒号前没有空格。

python - Python PLY 无法进行赋值操作