On Sat, 12 Nov 2005 10:46:53 +0100, Sybren Stuvel <[EMAIL PROTECTED]> wrote:
>Bengt Richter enlightened us with:
>> I suspect it's not possible to get '' in the list from
>> somestring.split()
>
>Time to adjust your suspicions:
>
>>>> ';abc;'.split(';')
>['', 'abc', '']
I know about that one ;-)
I meant somestring.split() just like that -- without a splitter argument.
My suspicion remains ;-)
>
>
>>> countDict[w] += 1
>>> else:
>>> countDict[w] = 1
>> does that beat the try and get versions? I.e., (untested)
>> try: countDict[w] += 1
>> except KeyError: countDict[w] = 1
>
>OPs way is faster. A 'try' block is very fast, but trowing & handling
>an exception is slow.
Yes, so it's data sensitive. Same with the other one not mentioned:
countDict.setdefault(w, [0])[0] += 1 # accum count in
length one list vs as int
# too much
subscripting work though
>
>> countDict[w] = countDict.get(w, 0) + 1
>
>I think this has the potential of being faster than OPs method,
>because it's likely to be fully implemented in C.
>
Not sure what you mean. Don't forget, all those expressions are evaluated
dynamically
step by step with byte codes being switched on in c, but still a bunch of
steps. I.e.,
>>> import dis
>>> dis.dis(compile('countDict[w] = countDict.get(w, 0) + 1', '', 'exec'))
1 0 LOAD_NAME 0 (countDict)
3 LOAD_ATTR 1 (get)
6 LOAD_NAME 2 (w)
9 LOAD_CONST 0 (0)
12 CALL_FUNCTION 2
15 LOAD_CONST 1 (1)
18 BINARY_ADD
19 LOAD_NAME 0 (countDict)
22 LOAD_NAME 2 (w)
25 STORE_SUBSCR
26 LOAD_CONST 2 (None)
29 RETURN_VALUE
Looks like if you succeed most of the time without a KeyError, the try/except
might be
a tad faster, depending on what the exception block setup/teardown costs.
>>> dis.dis(compile("""\
... try: countDict[w] += 1
... except KeyError: countDict[w] = 1
... """, '', 'exec'))
1 0 SETUP_EXCEPT 20 (to 23)
3 LOAD_NAME 0 (countDict)
6 LOAD_NAME 1 (w)
9 DUP_TOPX 2
12 BINARY_SUBSCR
13 LOAD_CONST 0 (1)
16 INPLACE_ADD
17 ROT_THREE
18 STORE_SUBSCR
19 POP_BLOCK
20 JUMP_FORWARD 29 (to 52)
2 >> 23 DUP_TOP
24 LOAD_NAME 2 (KeyError)
27 COMPARE_OP 10 (exception match)
30 JUMP_IF_FALSE 17 (to 50)
33 POP_TOP
34 POP_TOP
35 POP_TOP
36 POP_TOP
37 LOAD_CONST 0 (1)
40 LOAD_NAME 0 (countDict)
43 LOAD_NAME 1 (w)
46 STORE_SUBSCR
47 JUMP_FORWARD 2 (to 52)
>> 50 POP_TOP
51 END_FINALLY
>> 52 LOAD_CONST 1 (None)
55 RETURN_VALUE
Regards,
Bengt Richter
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