Merge pull request #95 from AWhetter/fix_52

Can supply a default return value to get()

Author: calebcase

dpath/util.py

@@ -4,11 +4,11 @@
 from dpath.exceptions import InvalidKeyName
 import dpath.segments
 
+_DEFAULT_SENTINAL = object()
 MERGE_REPLACE = (1 << 1)
 MERGE_ADDITIVE = (1 << 2)
 MERGE_TYPESAFE = (1 << 3)
 
-
 def __safe_path__(path, separator):
     '''
     Given a path and separator, return a tuple of segments. If path is
@@ -145,13 +145,15 @@ def f(obj, pair, counter):
     return changed
 
 
-def get(obj, glob, separator='/'):
+def get(obj, glob, separator='/', default=_DEFAULT_SENTINAL):
     '''
     Given an object which contains only one possible match for the given glob,
     return the value for the leaf matching the given glob.
+    If the glob is not found and a default is provided,
+    the default is returned.
 
     If more than one leaf matches the glob, ValueError is raised. If the glob is
-    not found, KeyError is raised.
+    not found and a default is not provided, KeyError is raised.
     '''
     if glob == '/':
         return obj
@@ -169,6 +171,9 @@ def f(obj, pair, results):
     results = dpath.segments.fold(obj, f, [])
 
     if len(results) == 0:
+        if default  is not _DEFAULT_SENTINAL:
+            return default
+
         raise KeyError(glob)
     elif len(results) > 1:
         raise ValueError("dpath.util.get() globs must match only one leaf : %s" % glob)

tests/test_util_get_values.py

@@ -28,6 +28,9 @@ def test_get_explicit_single():
 
     assert(dpath.util.get(ehash, '/a/b/c/f') == 2)
     assert(dpath.util.get(ehash, ['a', 'b', 'c', 'f']) == 2)
+    assert(dpath.util.get(ehash, ['a', 'b', 'c', 'f'], default=5) == 2)
+    assert(dpath.util.get(ehash, ['does', 'not', 'exist'], default=None) is None)
+    assert(dpath.util.get(ehash, ['doesnt', 'exist'], default=5) == 5)
 
 
 def test_get_glob_single():
@@ -45,6 +48,8 @@ def test_get_glob_single():
 
     assert(dpath.util.get(ehash, '/a/b/*/f') == 2)
     assert(dpath.util.get(ehash, ['a', 'b', '*', 'f']) == 2)
+    assert(dpath.util.get(ehash, ['a', 'b', '*', 'f'], default=5) == 2)
+    assert(dpath.util.get(ehash, ['doesnt', '*', 'exist'], default=6) == 6)
 
 
 def test_get_glob_multiple():
@@ -63,6 +68,7 @@ def test_get_glob_multiple():
 
     assert_raises(ValueError, dpath.util.get, ehash, '/a/b/*/d')
     assert_raises(ValueError, dpath.util.get, ehash, ['a', 'b', '*', 'd'])
+    assert_raises(ValueError, dpath.util.get, ehash, ['a', 'b', '*', 'd'], default=3)
 
 
 def test_get_absent():