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<title>5.15.4 Comparison to the built-in set types
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<H2><A NAME=
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5.15.4 Comparison to the built-in
<tt class=
"class">set
</tt> types
The built-in
<tt class=
"class">set
</tt> and
<tt class=
"class">frozenset
</tt> types were designed based
on lessons learned from the
<tt class=
"module">sets
</tt> module. The key differences are:
<LI><tt class=
"class">Set
</tt> and
<tt class=
"class">ImmutableSet
</tt> were renamed to
<tt class=
"class">set
</tt> and
<tt class=
"class">frozenset
</tt>.
<LI>There is no equivalent to
<tt class=
"class">BaseSet
</tt>. Instead, use
<code>isinstance(x, (set, frozenset))
</code>.
<LI>The hash algorithm for the built-ins performs significantly better
(fewer collisions) for most datasets.
<LI>The built-in versions have more space efficient pickles.
<LI>The built-in versions do not have a
<tt class=
"method">union_update()
</tt> method.
Instead, use the
<tt class=
"method">update()
</tt> method which is equivalent.
<LI>The built-in versions do not have a
<tt class=
"method">_repr(sort=True)
</tt> method.
Instead, use the built-in
<tt class=
"function">repr()
</tt> and
<tt class=
"function">sorted()
</tt>
functions:
<code>repr(sorted(s))
</code>.
<LI>The built-in version does not have a protocol for automatic conversion
to immutable. Many found this feature to be confusing and no one
in the community reported having found real uses for it.
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<span class=
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2.4.2, documentation updated on
28 September
2005.
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