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Diffstat (limited to 'Doc/lib/libsets.tex')
| -rw-r--r-- | Doc/lib/libsets.tex | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/Doc/lib/libsets.tex b/Doc/lib/libsets.tex index 8085ab1d48..0cd5e2e283 100644 --- a/Doc/lib/libsets.tex +++ b/Doc/lib/libsets.tex @@ -30,7 +30,10 @@ method but omits methods which alter the contents of the set. Both abstract class useful for determining whether something is a set: \code{isinstance(\var{obj}, BaseSet)}. -The set classes are implemented using dictionaries. As a result, sets +The set classes are implemented using dictionaries. Accordingly, the +requirements for set elements are the same as those for dictionary keys; +namely, that the element defines both \method{__eq__} and \method{__hash__}. +As a result, sets cannot contain mutable elements such as lists or dictionaries. However, they can contain immutable collections such as tuples or instances of \class{ImmutableSet}. For convenience in implementing |