gerrit.onap Code Review - sdc/sdc-distribution-client.git/blob

   1 """A collection of modules for iterating through different kinds of
   2 tree, generating tokens identical to those produced by the tokenizer
   3 module.
   4
   5 To create a tree walker for a new type of tree, you need to do
   6 implement a tree walker object (called TreeWalker by convention) that
   7 implements a 'serialize' method taking a tree as sole argument and
   8 returning an iterator generating tokens.
   9 """
  10
  11 from __future__ import absolute_import, division, unicode_literals
  12
  13 import sys
  14
  15 from ..utils import default_etree
  16
  17 treeWalkerCache = {}
  18
  19
  20 def getTreeWalker(treeType, implementation=None, **kwargs):
  21     """Get a TreeWalker class for various types of tree with built-in support
  22
  23     treeType - the name of the tree type required (case-insensitive). Supported
  24                values are:
  25
  26                 "dom" - The xml.dom.minidom DOM implementation
  27                 "pulldom" - The xml.dom.pulldom event stream
  28                 "etree" - A generic walker for tree implementations exposing an
  29                           elementtree-like interface (known to work with
  30                           ElementTree, cElementTree and lxml.etree).
  31                 "lxml" - Optimized walker for lxml.etree
  32                 "genshi" - a Genshi stream
  33
  34     implementation - (Currently applies to the "etree" tree type only). A module
  35                       implementing the tree type e.g. xml.etree.ElementTree or
  36                       cElementTree."""
  37
  38     treeType = treeType.lower()
  39     if treeType not in treeWalkerCache:
  40         if treeType in ("dom", "pulldom"):
  41             name = "%s.%s" % (__name__, treeType)
  42             __import__(name)
  43             mod = sys.modules[name]
  44             treeWalkerCache[treeType] = mod.TreeWalker
  45         elif treeType == "genshi":
  46             from . import genshistream
  47             treeWalkerCache[treeType] = genshistream.TreeWalker
  48         elif treeType == "lxml":
  49             from . import lxmletree
  50             treeWalkerCache[treeType] = lxmletree.TreeWalker
  51         elif treeType == "etree":
  52             from . import etree
  53             if implementation is None:
  54                 implementation = default_etree
  55             # XXX: NEVER cache here, caching is done in the etree submodule
  56             return etree.getETreeModule(implementation, **kwargs).TreeWalker
  57     return treeWalkerCache.get(treeType)