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Don't use the confusing term "set membership".

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Georg Brandl 2008-03-28 12:24:51 +00:00
parent 8ca6c84b6f
commit 489343e948
1 changed files with 8 additions and 8 deletions
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Doc/reference/expressions.rst
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@ -1061,14 +1061,14 @@ Comparison of objects of the same type depends on the type:
another one is made arbitrarily but consistently within one execution of a
program.
The operators :keyword:`in` and :keyword:`not in` test for set membership. ``x
in s`` evaluates to true if *x* is a member of the set *s*, and false otherwise.
``x not in s`` returns the negation of ``x in s``. The set membership test has
traditionally been bound to sequences; an object is a member of a set if the set
is a sequence and contains an element equal to that object. However, it is
possible for an object to support membership tests without being a sequence. In
particular, dictionaries support membership testing as a nicer way of spelling
``key in dict``; other mapping types may follow suit.
The operators :keyword:`in` and :keyword:`not in` test for collection
membership. ``x in s`` evaluates to true if *x* is a member of the collection
*s*, and false otherwise. ``x not in s`` returns the negation of ``x in s``.
The collection membership test has traditionally been bound to sequences; an
object is a member of a collection if the collection is a sequence and contains
an element equal to that object. However, it make sense for many other object
types to support membership tests without being a sequence. In particular,
dictionaries (for keys) and sets support membership testing.
For the list and tuple types, ``x in y`` is true if and only if there exists an
index *i* such that ``x == y[i]`` is true.