[Tutor] Inherit from SyntaxError?

[Albert-Jan Roskam]

   On Mar 19, 2023 23:06, Cameron Simpson <cs at cskk.id.au> wrote:

     On 19Mar2023 10:30, Albert-Jan Roskam <sjeik_appie at hotmail.com> wrote:
     >   I'm writing a parser using Beazly's PLY package. I defined a custom
     >   exception (actually, two: one for the lexer and one for the parser).
     They
     >   inherit from SyntaxError. Along with a few other exceptions (e.g.
     >   MemoryError), I've always regarded SyntaxError as "special". Are
     there any
     >   disadvantages to inheriting from SyntaxError? I could also inherit
     from
     >   ValueError.

     Sounds good to me. I've got a class which inherits from SyntaxError:

          class ParseError(SyntaxError):
            ''' A ParseError subclasses SyntaxError in order to change the
     initialiser.
                This object has an additional attribute .context for the
     relevant FileContext
                (which has a .parent attribute).
            '''

            def __init__(self, context, offset, message, *a):
              ''' Initialise a ParseError given a FileContext and the offset
     into `context.text`.
                  Accept optional arguments `*a` after the `message`; if
     supplied these
                  are embedded into `message` with %-formatting.
              '''
              if a:
                message = message % a
              self.msg = message
              self.filename = context.filename
              self.lineno = context.lineno
              self.text = context.text
              self.offset = offset
              self.context = context

     I've had no problems, and it seems entirely sensible.

   ======
   Hi Alan, Cameron,
   Thanks! I now created one BaseParserError (inherits from SyntaxError) and
   a lexer + parser error (they each inherit from BaseParserError).
   So, is MemoryError the only really tricky exception? I mean, the
   interpreter might just die before it is able to recover from the
   MemoryError?
   Best wishes,
   Albert-Jan