[Notes] [Git][BuildStream/buildstream][danielsilverstone-ct/further-optimisations] _yaml.py: Reduce use of `isinstance()` in `node_sanitize()`

[Daniel Silverstone <gitlab mg gitlab com>]

Title: GitLab

Daniel Silverstone pushed to branch danielsilverstone-ct/further-optimisations at BuildStream / buildstream

Commits:

• 73c18504
  by Daniel Silverstone at 2018-11-06T13:41:09Z

  _yaml.py: Reduce use of `isinstance()` in `node_sanitize()`
  
  We know that nodes are typically one of:
  str, list, dict, bool, tuple, NoneType or our ChainMap
  Of these, dict and ChainMap are Mapping, only list is list
  and the rest are returned unchanged.  We can reduce/defer our use
  of isinstance here, dramatically, improving performance.
  
  Signed-off-by: Daniel Silverstone <daniel silverstone codethink co uk>
  

1 changed file:

• buildstream/_yaml.py

Changes:

buildstream/_yaml.py

---

...	...	@@ -914,9 +914,21 @@ RoundTripRepresenter.add_representer(SanitizedDict,
914	914	# Only dicts are ordered, list elements are left in order.
915	915	#
916	916	def node_sanitize(node):
	917	+ # Short-circuit None which occurs ca. twice per element
	918	+ if node is None:
	919	+ return node
	920	+
	921	+ node_type = type(node)
	922	+ # Next short-circuit integers, floats, strings, booleans, and tuples
	923	+ if node_type in (int, float, str, bool, tuple):
	924	+ return node
	925	+ # Now short-circuit lists
	926	+ elif node_type is list:
	927	+ return [node_sanitize(elt) for elt in node]
917	928
918		- if isinstance(node, collections.Mapping):
919		-
	929	+ # Finally ChainMap and dict, and other Mappings need special handling
	930	+ if (node_type in (dict, ChainMap) or
	931	+ isinstance(node, collections.Mapping)):
920	932	result = SanitizedDict()
921	933
922	934	key_list = [key for key, _ in node_items(node)]
...	...	@@ -924,10 +936,10 @@ def node_sanitize(node):
924	936	result[key] = node_sanitize(node[key])
925	937
926	938	return result
927		-
928	939	elif isinstance(node, list):
929	940	return [node_sanitize(elt) for elt in node]
930	941
	942	+ # Everything else (such as commented scalars) just gets returned as-is.
931	943	return node
932	944
933	945

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