On 06/03/2023 11.59, aapost wrote:
On 3/5/23 17:43, Stefan Ram wrote:
The following behaviour of Python strikes me as being a bit
"irregular". A user tries to chop of sections from a string,
but does not use "split" because the separator might become
more complicated so that a regular expression will be required
to find it. But for now, let's use a simple "find":
|>>> s = 'alpha.beta.gamma'
|>>> s[ 0: s.find( '.', 0 )]
|'alpha'
|>>> s[ 6: s.find( '.', 6 )]
|'beta'
|>>> s[ 11: s.find( '.', 11 )]
|'gamm'
|>>>
. The user always inserted the position of the previous find plus
one to start the next "find", so he uses "0", "6", and "11".
But the "a" is missing from the final "gamma"!
And it seems that there is no numerical value at all that
one can use for "n" in "string[ 0: n ]" to get the whole
string, isn't it?
I would agree with 1st part of the comment.
Just noting that string[11:], string[11:None], as well as string[11:16]
work ... as well as string[11:324242]... lol..
To expand on the above, answering the OP's second question: the numeric
value is len( s ).
If the repetitive process is required, try a loop like:
>>> start_index = 11 #to cure the issue-raised
>>> try:
... s[ start_index:s.index( '.', start_index ) ]
... except ValueError:
... s[ start_index:len( s ) ]
...
'gamma'
However, if the objective is to split, then use the function built for
the purpose:
>>> s.split( "." )
['alpha', 'beta', 'gamma']
(yes, the OP says this won't work - but doesn't show why)
If life must be more complicated, but the next separator can be
predicted, then its close-relative is partition().
NB can use both split() and partition() on the sub-strings produced by
an earlier split() or ... ie there may be no reason to work strictly
from left to right
- can't really help with this because the information above only shows
multiple "." characters, and not how multiple separators might be
interpreted.
A straight-line approach might be to use maketrans() and translate() to
convert all the separators to a single character, eg white-space, which
can then be split using any of the previously-mentioned methods.
If the problem is sufficiently complicated and the OP is prepared to go
whole-hog, then PSL's tokenize library or various parser libraries may
be worth consideration...
--
Regards,
=dn
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