A query about list

[Tony Clarke]

"Robert Brewer" <fumanchu at amor.org> wrote in message news:<mailman.25.1065948762.2192.python-list at python.org>...
> If you're going to gloss over all errors *and* just print, this works in
> Python 2.2:
> 
> >>> def depth(seq):
> ... 	for item in seq:
> ... 		try: depth(item)
> ... 		except: print item,
> ... 		
> >>> a = [1,[2,3,4],5,6,7,[8,9,10],11,12]
> >>> depth(a)
>  1 2 3 4 5 6 7 8 9 10 11 12
> >>> a = [1,[2,3,4],5,6,7,['mangos in syrup',9,10],11,12]
> >>> depth(a)
>  1 2 3 4 5 6 7 m a n g o s   i n   s y r u p 9 10 11 12
> 
> You don't need "continue" or "len".
> 
> Robert Brewer
> MIS
> Amor Ministries
> fumanchu at amor.org
> 
> > -----Original Message-----
> > From: Tony Clarke [mailto:a.clarke11 at ntlworld.com] 
> > Sent: Sunday, October 12, 2003 1:40 AM
> > To: python-list at python.org
> > Subject: Re: A query about list
> > 
> > 
> > "Robert Brewer" <fumanchu at amor.org> wrote in message 
> > news:<mailman.1065733220.31901.python-list at python.org>...
> > > Dave Benjamin wrote:
> > > > Santanu Chatterjee wrote:
> > > > > I am very new to python. I have a query about 
> > > > > list in python.
> > > > > 
> > > > > Suppose I have a list 
> > > > > a = [1,[2,3,4],5,6,7,[8,9,10],11,12]
> > > > > I want to know if there is any simple python
> > > > > facility available that would expand the above list
> > > > > to give
> > > > > a = [1,2,3,4,5,6,7,8,9,10,11,12]
> > > > > 
> > > > Normally, I'd suggest "reduce(operator.add, ...)" to flatten 
> > > > a list, but
> > > > since you've got some "naked" entries, that won't work...
> > > > 
> > > > >>> def merge(x, y):
> > > > ...     if type(y) is type([]): return x + y
> > > > ...     return x + [y]
> > > > ...
> > > > >>> reduce(merge, a, [])
> > > > [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
> > > > 
> > > 
> > > Neat trick with the third parameter to reduce! Didn't know 
>  about that
> > > behavior. That cuts my long one-liner down from:
> > > 
> > > >>> reduce(lambda x, y: {type([]): x}.get(type(x), [x]) + {type([]):
> > > y}.get(type(y), [y]), a)
> > > 
> > > to just:
> > > 
> > > >>> reduce(lambda x, y: x + {type([]): y}.get(type(y), [y]), a, [])
> > > [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
> > > 
> > > /shudder. But it's fun. :)
> > > 
> > > 
> > > Robert Brewer
> > > MIS
> > > Amor Ministries
> > > fumanchu at amor.org
> > 
> > 
> > 
> > How about this single function (although not a single line:<), which
> > also works for any kind of sequence, and can cope with different types
> > in the sequence:
> > 
> > a = [1,[2,3,4],5,6,7,[8,9,10],11,12]
> > 
> > def depth(sequence):
> >   for item in sequence: 
> >    try:
> >      b=len(item) 
> >      depth(item)
> >    except:
> >     print item,
> >     continue
> >    
> > depth(a)
> > 
> > I think this is a precursor to generators, but I'm still on Python
> > 2.1.
> > -- 
> > http://mail.python.org/mailman/listinfo/python-list
> >

Thanks Robert,
Your code works in 2.1 as well, my code generated an exception during
iteration, yours generates an exception when iteration isn't possible.
Magic!