Array of Chars to String

[Michael Spencer]

Michael Spencer wrote:
> Bengt Richter wrote:
>  > I think this will be worth it if your string to modify is _very_ long:
> 
>>
>>  >>> def some_func(s, letters, table=''.join([chr(i) for i in 
>> xrange(256)])):
>>  ...     return s.translate(table,
>>  ...            ''.join([chr(i) for i in xrange(256) if chr(i) not in 
>> letters]))
>>  ...
>>  >>> some_func("Bob Carol Ted Alice", 'adB')
>>  'Bad'
>>
> According to my measurements the string doesn't have to be long at all 
> before your method is faster - cool use of str.translate:
> 
...and here's a version that appears faster than "".join across all lengths of 
strings:
  >>> import string
  >>> def some_func1(s, letters, table=string.maketrans("","")):
  ...     return s.translate(table, table.translate(table, letters))
  ...
  >>> some_func1("Bob Carol Ted Alice", "adB")
  'Bad'
  >>>

Timings follow:

  >>> def some_func(s, letters, table=''.join([chr(i) for i in xrange(256)])):
  ...     return s.translate(table,
  ...         ''.join([chr(i) for i in xrange(256) if chr(i) not in letters]))
  ...
  >>> def some_func1(s, letters, table=string.maketrans("","")):
  ...     return s.translate(table, table.translate(table, letters))
  ...
  >>> for multiplier in (1, 10, 100, 1000, 10000):
  ...     print "List multiplier: %s" % multiplier
  ...     print shell.timefunc(some_func, "Bob Carol Ted Alice" * multiplier, 'adB')
  ...     print shell.timefunc(some_func1, "Bob Carol Ted Alice" * multiplier, 
'adB')
  ...
  List multiplier: 1
  some_func(...)  1224 iterations, 408.57usec per call
  some_func1(...)  61035 iterations, 8.19usec per call
  List multiplier: 10
  some_func(...)  1223 iterations, 408.95usec per call
  some_func1(...)  54420 iterations, 9.19usec per call
  List multiplier: 100
  some_func(...)  1190 iterations, 420.48usec per call
  some_func1(...)  23436 iterations, 21.34usec per call
  List multiplier: 1000
  some_func(...)  951 iterations, 0.53msec per call
  some_func1(...)  3870 iterations, 129.21usec per call
  List multiplier: 10000
  some_func(...)  309 iterations, 1.62msec per call
  some_func1(...)  417 iterations, 1.20msec per call
  >>>