diff options
| -rw-r--r-- | Doc/library/stdtypes.rst | 15 |
1 files changed, 6 insertions, 9 deletions
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst index 04dd88803b..f0d51e26f2 100644 --- a/Doc/library/stdtypes.rst +++ b/Doc/library/stdtypes.rst @@ -1881,8 +1881,7 @@ Dictionary view objects The objects returned by :meth:`dict.keys`, :meth:`dict.values` and :meth:`dict.items` are *view objects*. They provide a dynamic view on the dictionary's entries, which means that when the dictionary changes, the view -reflects these changes. The keys and items views have a set-like character -since their entries +reflects these changes. Dictionary views can be iterated over to yield their respective data, and support membership tests: @@ -1910,8 +1909,11 @@ support membership tests: items (in the latter case, *x* should be a ``(key, value)`` tuple). -The keys and items views also provide set-like operations ("other" here refers -to another dictionary view or a set): +Keys views are set-like since their entries are unique and hashable. If all +values are hashable, so that (key, value) pairs are unique and hashable, then +the items view is also set-like. (Values views are not treated as set-like +since the entries are generally not unique.) Then these set operations are +available ("other" refers either to another view or a set): .. describe:: dictview & other @@ -1931,11 +1933,6 @@ to another dictionary view or a set): Return the symmetric difference (all elements either in *dictview* or *other*, but not in both) of the dictview and the other object as a new set. -.. warning:: - - Since a dictionary's values are not required to be hashable, any of these - four operations will fail if an involved dictionary contains such a value. - An example of dictionary view usage:: |