AFAIK使Python源代码词汇化的技术是：
当当前行的缩进级别小于前一行的缩进级别时，生成DEDENT。如果要关闭多个INDENT，则产生多个DEDENT。
当输入结束时，如果未关闭INDENT，则产生DEDENT。
现在，使用PLY：
如何从t_definition返回多个令牌？
到达EOF时如何调用t_definition？简单的\Z不起作用-PLY抱怨它匹配空字符串。
最佳答案
据我所知，PLY没有实现推送解析器接口，这是您最容易用bison解决此问题的方法。但是，注入自己的词法分析器包装器很容易，它可以处理dedent令牌队列。
最少的词法分析器实现需要实现一个token()方法，该方法返回具有type和value属性的对象。 （如果您的解析器使用它，则也需要它，但是我在这里不必担心。）
现在，让我们假设基础的（PLY生成的）词法分析器生成NEWLINE标记，其值是换行符后的前导空格的长度。如果某些行不参与INDENT / DEDENT算法，则应针对这些行取消NEWLINE；我们在这里不考虑这种情况。 lexer函数的一个简单示例（仅适用于空格，不适用于制表符）可能是：
# This function doesn't handle tabs. Beware!
def t_NEWLINE(self, t):
r'\n(?:\s*(?:[#].*)?\n)*\s*'
t.value = len(t.value) - 1 - t.value.rfind('\n')
return t
现在，我们用处理缩进的包装器包装PLY生成的词法分析器：
# WARNING:
# This code hasn't been tested much and it also may be inefficient
# and/or inexact. It doesn't do python-style tab handling. Etc. etc.
from collections import namedtuple, deque
# These are the tokens. We only generate one of each here. If
# we used lineno or didn't trust the parser to not mess with the
# token, we could generate a new one each time.
IndentToken = namedtuple('Token', 'type value')
dedent = IndentToken('DEDENT', None)
indent = IndentToken('INDENT', None)
newline= IndentToken('NEWLINE', None)
class IndentWrapper(object):
def __init__(self, lexer):
"""Create a new wrapper given the lexer which is being wrapped"""
self.lexer = lexer
self.indent_stack = [0]
# A queue is overkill for this case, but it's simple.
self.token_queue = deque()
# This is just in case the ply-generated lexer cannot be called again
# after it returns None.
self.eof_reached = False
def token(self):
"""Return the next token, or None if end of input has been reached"""
# Do we have any queued tokens?
if self.token_queue:
return self.token_queue.popleft()
# Are we done?
if self.eof_reached:
return None
# Get a token
t = self.lexer.token()
if t is None:
# At end of input, we might need to send some dedents
self.eof_reached = True
if len(self.indent_stack) > 1:
t = dedent
for i in range(len(self.indent_stack) - 1):
self.token_queue.append(dedent)
self.indent_stack = [0]
elif t.type == "NEWLINE":
# The NEWLINE token includes the amount of leading whitespace.
# Fabricate indent or dedents as/if necessary and queue them.
if t.value > self.indent_stack[-1]:
self.indent_stack.append(t.value)
self.token_queue.append(indent)
else:
while t.value < self.indent_stack[-1]:
self.indent_stack.pop()
self.token_queue.append(dedent)
if t.value != self.indent_stack[-1]:
raise IndentError # Or however you indicate errors
return t
关于python - PLY-返回多个 token ，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/28259366/