Source code for gavo.grammars.customgrammar

A grammar that imports a user-defined module and takes the RowIterator
from there.

The module has to define a RowIterator derived from CustomRowIterator.  It may
define a function makeDataPack receiving the grammar as its argument and
returning anything.  This anything will then be available as
self.grammar.dataPack to the row iterator.  Use this for expensive, one-time
preparations your row iterator has to perform.

#c Copyright 2008-2023, the GAVO project <>
#c This program is free software, covered by the GNU GPL.  See the
#c COPYING file in the source distribution.

from gavo import base
from gavo import rscdef
from gavo import utils
from gavo.grammars import common

_knownModules = {}

[docs]def getModuleName(): i = 0 while True: name = "usergrammar%d"%i if name not in _knownModules: _knownModules[name] = None return name
[docs]class CustomGrammar(common.Grammar, base.RestrictionMixin): """A Grammar with a user-defined row iterator taken from a module. See the `Writing Custom Grammars`_ (in the reference manual) for details. """ # To save on time when initializing the grammar (which happens at # RD parsing time), we delay initializing the user grammar to when # it's actually used (which happens much less frequently than loading # the RD). name_ = "customGrammar" _module = rscdef.ResdirRelativeAttribute("module", default=base.Undefined, description="Path to module containing your row iterator.", copyable=True) _isDispatching = base.BooleanAttribute("isDispatching", default=False, description="Is this a dispatching grammar (i.e., does the row iterator" " return pairs of role, row rather than only rows)?", copyable=True) def _initUserGrammar(self): self.userModule, _ = utils.loadPythonModule(self.module) self.rowIterator = self.userModule.RowIterator if hasattr(self.userModule, "makeDataPack"): self.dataPack = self.userModule.makeDataPack(self)
[docs] def parse(self, *args, **kwargs): if not hasattr(self, "userModule"): self._initUserGrammar() return common.Grammar.parse(self, *args, **kwargs)
[docs]class CustomRowIterator(common.RowIterator): """is a base class for custom row iterators. Implement at least _iterRows. And pass on any keyword args to __init__ to the next constructor. """