[Python-Dev] Remove str.find in 3.0?

Fri Aug 26 21:54:10 CEST 2005

Can str.find be listed in PEP 3000 (under builtins) for removal?
Would anyone really object?
Reasons:
1. Str.find is essentially redundant with str.index. The only difference 
is that str.index Pythonically indicates 'not found' by raising an 
exception while str.find does the same by anomalously returning -1. As 
best as I can remember, this is common for Unix system calls but unique 
among Python builtin functions. Learning and remembering both is a 
nuisance.
2. As is being discussed in a current c.l.p thread, -1 is a legal indexing 
subscript. If one uses the return value as a subscript without checking, 
the bug is not caught. None would be a better return value should find not 
be deleted.
3. Anyone who prefers to test return values instead of catch exceptions can 
write (simplified, without start,end params):
def sfind(string, target):
 try:
 return string.index(target)
 except ValueError:
 return None # or -1 for back compatibility, but None better
This can of course be done for any function/method that indicates input 
errors with exceptions instead of a special return value. I see no reason 
other than history that this particular method should be doubled.
If .find is scheduled for the dustbin of history, I would be willing to 
suggest doc and docstring changes. (str.index.__doc__ currently refers to 
str.find.__doc__. This should be reversed.)
Terry J. Reedy