Dair Dair -4 years ago 158
Python Question

Using a dollar sign in enum (pypeg)?

I want to match types of the form either

$f
,
$c
, ...,
$d
using pypeg, so I tried putting it in an
Enum
as follows:

class StatementType(Keyword):
grammar = Enum( K("$f"), K("$c"),
K("$v"), K("$e"),
K("$a"), K("$p"),
K("$d"))


However, this fails:

>>> k = parse("$d", StatementType)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python3.6/site-packages/pypeg2/__init__.py", line 667, in parse
t, r = parser.parse(text, thing)
File "/usr/local/lib/python3.6/site-packages/pypeg2/__init__.py", line 794, in parse
raise r
File "<string>", line 1
$d
^
SyntaxError: expecting StatementType


I have also tried replacing the
$x
with
\$x
to escape the
$
character. I also tried prepending
r"\$x"
in hopes that it treats it as a regex object. Neither of these combinations seem to work and give the same error message. How do I get it to match the example I gave?

Answer Source

The default regex for Keywords is \w+. You can change it by setting the Keyword.regex class variable:

class StatementType(Keyword):
    grammar = Enum( K("$f"), K("$c"),
                    K("$v"), K("$e"),
                    K("$a"), K("$p"),
                    K("$d"))

Keyword.regex = re.compile(r"\$\w") # e.g. $a, $2, $_
k = parse("$d", StatementType)
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