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diff --git a/Doc/glossary.rst b/Doc/glossary.rst index dfcbee8..aa69867 100644 --- a/Doc/glossary.rst +++ b/Doc/glossary.rst @@ -140,6 +140,20 @@ Glossary in the past to create a "free-threaded" interpreter (one which locks shared data at a much finer granularity), but performance suffered in the common single-processor case. + + hashable + An object is *hashable* if it has a hash value that never changes during + its lifetime (it needs a :meth:`__hash__` method), and can be compared to + other objects (it needs an :meth:`__eq__` or :meth:`__cmp__` method). + Hashable objects that compare equal must have the same hash value. + + Hashability makes an object usable as a dictionary key and a set member, + because these data structures use the hash value internally. + + All of Python's immutable built-in objects are hashable, while all mutable + containers (such as lists or dictionaries) are not. Objects that are + instances of user-defined classes are hashable by default; they all + compare unequal, and their hash value is their :func:`id`. IDLE An Integrated Development Environment for Python. IDLE is a basic editor |