> Is there any significant performance difference between the
> tests, ``key in dictionary'' and ``dictionary.has_key(key)''?
> I would prefer using the ``key in'' because it's a bit easier to
> type, and can also be used with lists in addition to dictionaries.
Dunno about speed, but they do disassemble slightly differently:
>>> import dis
>>> a={1:2, 3:4}
>>> def x():
... if 3 in a:
... print "3 in"
...
>>> def y():
... if a.has_key(3):
... print "3 has"
...
>>> dis.dis(x)
2 0 LOAD_CONST 1 (3)
3 LOAD_GLOBAL 0 (a)
6 COMPARE_OP 6 (in)
9 JUMP_IF_FALSE 9 (to 21)
12 POP_TOP
3 13 LOAD_CONST 2 ('3 in')
16 PRINT_ITEM
17 PRINT_NEWLINE
18 JUMP_FORWARD 1 (to 22)
>> 21 POP_TOP
>> 22 LOAD_CONST 0 (None)
25 RETURN_VALUE
>>> dis.dis(y)
2 0 LOAD_GLOBAL 0 (a)
3 LOAD_ATTR 1 (has_key)
6 LOAD_CONST 1 (3)
9 CALL_FUNCTION 1
12 JUMP_IF_FALSE 9 (to 24)
15 POP_TOP
3 16 LOAD_CONST 2 ('3 has')
19 PRINT_ITEM
20 PRINT_NEWLINE
21 JUMP_FORWARD 1 (to 25)
>> 24 POP_TOP
>> 25 LOAD_CONST 0 (None)
28 RETURN_VALUE
Alan
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