On Sat, 21 Jul 2007 09:22:32 +0530, Rustom Mody wrote
> Can someone who knows about python internals throw some light on why
> >>> x in dic
> is cheaper than
> >>> dic.has_key(x)
>
> ??
I won't claim to know Python internals, but compiling and disassembling the
expressions in question reveals the reason:
>>> from compiler import compile
>>> from dis import dis
>>> dis(compile("dic.has_key(x)","","eval"))
1 0 LOAD_NAME 0 (dic)
3 LOAD_ATTR 1 (has_key)
6 LOAD_NAME 2 (x)
9 CALL_FUNCTION 1
12 RETURN_VALUE
>>> dis(compile("x in dic","","eval"))
1 0 LOAD_NAME 0 (x)
3 LOAD_NAME 1 (dic)
6 COMPARE_OP 6 (in)
9 RETURN_VALUE
"dic.has_key(x)" goes through an attribute lookup to find the function that
looks for the key. "x in dic" finds the function more directly.
--
Carsten Haese
http://informixdb.sourceforge.net
--
http://mail.python.org/mailman/listinfo/python-list
