On 15/03/2016 00:25, BartC wrote:
> On 14/03/2016 23:24, Steven D'Aprano wrote:
>> Try this instead:
>>
>> c = chr(c)
>> if 'A' <= c <= 'Z':
>> upper += 1
>> elif 'a' <= c <= 'z':
>> lower += 1
>> elif '0' <= c <= '9':
>> digits += 1
>> else:
>> other += 1
>>
>>
>> But even better:
>>
>> if c.isupper():
>> upper += 1
>> elif c islower():
>> lower += 1
>> elif c.isdigit():
>> digits += 1
>> else:
>> other += 1
>>
>>
>> which will work correctly for non-ASCII characters as well.
>
> Yes, but now you've destroyed my example!
>
> A more realistic use of switch is shown below [not Python].
A tokeniser along those lines in Python, with most of the bits filled
in, is here:
http://pastebin.com/dtM8WnFZ
This is a test of a character-at-a-time task in Python; I know such
tasks are not popular here, but exactly such tasks are what I often use
dynamic languages for.
I started off trying to write it in a more efficient way that would suit
Python better, but quickly tired of that. I should be able to express
the code how I want.
But it is based on strings (integers seem to be slower in Python), and
uses your style above.
However, this is crying out for at least a case statement (which works
with anything) if not a switch that works with ints and constants.
All other versions it is compared against use switches, integers, and
names that don't change at runtime.
---------------------------------------------------------------------
Performance figures for the test code above. These use the same input
file (220K lines of CPython C sources), and show lines-per-second
achieved not runtime.
Interpreters:
Py2 Python 2 (various)
Py3 Python 3.4
PyPy PyPy 3.2.5
PCA Mine (accelerated via some ASM routines, 64-bit)
PCC Mine (standard, 32-bit)
Windows 7 64-bits:
Py3: 33K lps (lines per second)
Py2: 43K lps
PyPy 100K lps
PCC: 460K lps
C: 1000K lps (Tiny C compiler, native code)
PCA: 1200K lps
B: 5800K Lps (My own compiler, native code)
C: 9000K lps (gcc C compiler, native code)
(Tiny C is particularly poor at generating code for switches. Still,
native code is running slower than byte-code, which is something.)
Ubuntu 15.x 64-bits (run via VirtualBox on Windows 7):
Py2: 58K lps
PyPy: 133K lps (2.x)
PCC: 250-330K lps (via 'wine'; timings variable)
PCA: 500-800K lps (via 'wine')
(Debian on an old Raspberry Pi:
Py2: 2K lps
PCC: 16K lps
I think these, especially for PCC, should be faster. But this was a
hastily created Linux port of PCC.)
--
Bartc
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