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Add a note reminding the reader that sets are not sequences. I 

received feedback that was based in the misunderstanding that sets
were sequences.
This commit is contained in:
Guido van Rossum 2002-08-20 20:05:23 +00:00
parent 0bd7832285
commit 290f1870f1
1 changed files with 10 additions and 0 deletions
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10
Lib/sets.py
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@ -4,6 +4,16 @@ This module implements sets using dictionaries whose values are
ignored. The usual operations (union, intersection, deletion, etc.)
are provided as both methods and operators.
Important: sets are not sequences! While they support 'x in s',
'len(s)', and 'for x in s', none of those operations are unique for
sequences; for example, mappings support all three as well. The
characteristic operation for sequences is subscripting with small
integers: s[i], for i in range(len(s)). Sets don't support
subscripting at all. Also, sequences allow multiple occurrences and
their elements have a definite order; sets on the other hand don't
record multiple occurrences and don't remember the order of element
insertion (which is why they don't support s[i]).
The following classes are provided:
BaseSet -- All the operations common to both mutable and immutable