[Python-Dev] Chaining seq1.pop().extend(seq2) does give wrong result

[Sjoerd Mullender]

Jacek Trzmiel wrote:
> Hi,
> 
> $ python
> Python 2.3.2 (#1, Dec  5 2003, 03:04:50) 
> [GCC 3.3.3 [FreeBSD] 20031106] on freebsd5
> Type "help", "copyright", "credits" or "license" for more information.
> 
>>>>stack = [[1], [2]]
>>>>fields = [3]
>>>>out = stack.pop()
>>>>out.extend(fields)
>>>>print out
> 
> [2, 3]
> 
>>>>stack = [[1], [2]]
>>>>fields = [3]
>>>>out = stack.pop().extend(fields)
>>>>print out
> 
> None
> 
> 
> Shouldn't those two give identical result?

No.  somelist.extend() changes somelist but doesn't return a value (in 
other words, it returns None, which is exactly what you're seeing).

Also, this is not really appropriate for python-dev, but rather for 
python-list, I would think.

-- 
Sjoerd Mullender <sjoerd at acm.org>