[Tutor] String.find won't - why?

[Michael P. Reilly]

On Mon, Oct 29, 2001 at 12:04:17AM +0100, Danny Kohn wrote:
> Am trying to remove all 0D 0A (Hex). Thought this was done through the following while loop.
> The file is attached.
> The first round things works nicely. The 0D 0A (Hex) is found and removed. Pos is correctly 142.
> The second round things behave more strangely. Pos will get a wrong value (178) but there just is no 0D 0A (Hex) there and so the i:pos string will get to short.

[other code snipped]
> 
> i=0
> a =  ''
> while i < len(text):
> 	pos = string.find(text[i:], '\n')
> 	print pos
> 	if pos > 0:
> 		a = a + text[i:pos]
> 		print a
> 		print
> 	i = i + pos + 1

In addition to Remco's comments, the find function also takes an optional
third argument which is the starting place.

i = 0
a = ''
while i < len(text):
  pos = string.find(text, '\n', i)
  # now, pos is either -1 or greater than i
  print pos
  if pos > 0:
    a = a + text[i:pos]
    print a
    print
  else:
    break # no more newlines found
  i = pos + 1

Since the new position is based on the previous position, we will always
get a proper substring (unless you get a -1 ;), this also means that
the new position can be used directly for the next time around.

  -Arcege

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| Michael P. Reilly                | arcege@speakeasy.net              |
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