Source Code for Module gavo.grammars.customgrammar

 1  """ 
 2  A grammar that imports a user-defined module and takes the RowIterator 
 3  from there. 
 4   
 5  The module has to define a RowIterator derived from CustomRowIterator.  It may 
 6  define a function makeDataPack receiving the grammar as its argument and 
 7  returning anything.  This anything will then be available as 
 8  self.grammar.dataPack to the row iterator.  Use this for expensive, one-time 
 9  preparations your row iterator has to perform. 
10  """ 
11   
12  #c Copyright 2008-2019, the GAVO project 
13  #c 
14  #c This program is free software, covered by the GNU GPL.  See the 
15  #c COPYING file in the source distribution. 
16   
17   
18  from gavo import base 
19  from gavo import rscdef 
20  from gavo import utils 
21  from gavo.grammars import common 
22   
23   
24  _knownModules = {} 
25   
26   
27 -def getModuleName(): 
28          i = 0 
29          while True: 
30                  name = "usergrammar%d"%i 
31                  if name not in _knownModules: 
32                          _knownModules[name] = None 
33                          return name 
34   
35   
36 -class CustomGrammar(common.Grammar, base.RestrictionMixin): 
37          """A Grammar with a user-defined row iterator taken from a module. 
38   
39          See the `Writing Custom Grammars`_ (in the reference manual) for details. 
40          """ 
41  #       To save on time when initializing the grammar (which happens at 
42  #       RD parsing time), we delay initializing the user grammar to when 
43  #       it's actually used (which happens much less frequently than loading 
44  #       the RD). 
45   
46          name_ = "customGrammar" 
47   
48          _module = rscdef.ResdirRelativeAttribute("module", default=base.Undefined, 
49                  description="Path to module containing your row iterator.", copyable=True) 
50          _isDispatching = base.BooleanAttribute("isDispatching", default=False, 
51                  description="Is this a dispatching grammar (i.e., does the row iterator" 
52                  " return pairs of role, row rather than only rows)?", copyable=True) 
53   
54 -        def _initUserGrammar(self): 
55                  self.userModule, _ = utils.loadPythonModule(self.module) 
56                  self.rowIterator = self.userModule.RowIterator 
57                  if hasattr(self.userModule, "makeDataPack"): 
58                          self.dataPack = self.userModule.makeDataPack(self) 
59   
60 -        def parse(self, *args, **kwargs): 
61                  if not hasattr(self, "userModule"): 
62                          self._initUserGrammar() 
63                  return common.Grammar.parse(self, *args, **kwargs) 
64   
65   
66 -class CustomRowIterator(common.RowIterator): 
67          """is a base class for custom row iterators. 
68   
69          Implement at least _iterRows.  And pass on any keyword args to __init__ 
70          to the next constructor. 
71          """ 
72