[ python-Bugs-811604 ] "string".split behaviour for empty strings

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Bugs item #811604, was opened at 2003-09-24 04:20
Message generated for change (Comment added) made by mondragon
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Category: Python Interpreter Core
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: T.Meyarivan (meyarivan)
Assigned to: Nobody/Anonymous (nobody)
Summary: "string".split behaviour for empty strings

Initial Comment:

"".split() -> []

"".split(' ') -> ['']

It is not clear from the documentation as to what is
the defined behaviour in the above case. To say the
least, it is 
completely counter-intuitive..(splitting an empty
string should
return the list [''] in both cases).

>From stringobject.c, the behaviour of split_whitespace
(i.e split called without sep) and string_split (split
called with sep) is different for empty
strings..perhaps the function split_whitespace needs to
be patched.

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>Comment By: Nick Bastin (mondragon)
Date: 2004-03-21 12:11

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Fixed in doc/lib/libstring.tex version 1.57

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Comment By: Terry J. Reedy (tjreedy)
Date: 2003-09-28 19:50

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Suggestion: find section of Lib Ref discussing str.split, quote 
existing def, and add succinct sentence that you think is 
needed.  Then change category to 'documentation' so 
appropriate person(s) will see proposal.

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Comment By: T.Meyarivan (meyarivan)
Date: 2003-09-26 07:04

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Thats so counter intuitive.. :-(

At least the documentation should specify the fact that the
behaviour of "string".split for empty strings is so and so....

The reason this probably never came up ( or mostly ignored
by majority ) is that people probably check if the string is
empty before proceeding to process it.. 

I am not closing the bug before the specific behaviour of
"string".split for empty strings gets to the docs..

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Comment By: Raymond Hettinger (rhettinger)
Date: 2003-09-26 00:35

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And so it is.  The whitespace version (no args) and the
specified separator version work differently -- the second
version can never return an empty list.

This code has been around for a good while and it is likely
that much code relies on the behavior, so I recommend
classifying it as a beauty spot and closing the bug.

"One man's bug is another man's feature"


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Comment By: T.Meyarivan (meyarivan)
Date: 2003-09-24 04:51

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"".split(None) -> [] 

which is expected because in the case when no sep is
specified and when sep == None, split_whitespace is called..

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