Source Code for Module gavo.base.common

 1  """ 
 2  Common code for DaCHS's base package. 
 3  """ 
 4   
 5  #c Copyright 2008-2019, the GAVO project 
 6  #c 
 7  #c This program is free software, covered by the GNU GPL.  See the 
 8  #c COPYING file in the source distribution. 
 9   
10   
11  from __future__ import print_function 
12   
13  from gavo.utils.excs import *  #noflake: really want those names 
14  from gavo.utils import excs # make life a bit easier for pyflakes. 
15   
16   
17 -class NotGivenType(type): 
18 -        def __str__(self): 
19                  raise excs.StructureError( 
20                          "%s cannot be stringified"%self.__class__.__name__) 
21   
22          __unicode__ = __str__ 
23   
24 -        def __repr__(self): 
25                  return "<Not given/empty>" 
26   
27 -        def __nonzero__(self): 
28                  return False 
29   
30   
31 -class NotGiven(object): 
32          """A sentinel class for defaultless values that can remain undefined. 
33          """ 
34          __metaclass__ = NotGivenType 
35   
36   
37 -class Ignore(excs.ExecutiveAction): 
38          """An executive action causing an element to be not adopted by its 
39          parent. 
40   
41          Raise this in -- typically -- onElementComplete if the element just 
42          built goes somewhere else but into its parent structure (or is 
43          somehow benignly unusable).  Classic use case: Active Tags. 
44          """ 
45   
46   
47 -class Replace(excs.ExecutiveAction): 
48          """An executive action replacing the current child with the Exception's 
49          argument. 
50   
51          Use this sparingly.  I'd like to get rid of it. 
52          """ 
53 -        def __init__(self, newOb, newName=None): 
54                  self.newOb, self.newName = newOb, newName 
55   
56   
57 -class Parser(object): 
58          """is an object that routes events. 
59   
60          It is constructed with up to three functions for handling start, 
61          value, and end events; these would override methods start_, end_, 
62          or value_.  Thus, you can simply implement when inheriting from 
63          Parser.  In that case, no call the the constructor is necessary 
64          (i.e., Parser works as a mixin as well). 
65          """ 
66 -        def __init__(self, start=None, value=None, end=None): 
67                  self.start, self.value, self.end = start, value, end 
68           
69 -        def feedEvent(self, ctx, type, name, value): 
70                  if type=="start": 
71                          return self.start_(ctx, name, value) 
72                  elif type=="value": 
73                          return self.value_(ctx, name, value) 
74                  elif type=="end": 
75                          return self.end_(ctx, name, value) 
76                  else: 
77                          raise excs.StructureError( 
78                                  "Illegal event type while building: '%s'"%type) 
79   
80   
81 -class StructParseDebugMixin(object): 
82          """put this before Parser in the parent class list of a struct, 
83          and you'll see the events coming in to your parser. 
84          """ 
85 -        def feedEvent(self, ctx, type, name, value): 
86                  print(type, name, value, self) 
87                  return Parser.feedEvent(self, ctx, type, name, value) 
88