brain stuck. whats occurring here?

[mensanator at aol.com]

On Feb 7, 11:38 am, Matthew_WAR... at bnpparibas.com wrote:
> Hallo,
>
> I'm after
>
> [[[],[],[],[],[]],[[],[],[],[],[]],[[],[],[],[],[]],[[],[],[],[],[]],[[],[]­,[],[],[]]]
>
> (NxN 'grid', 5x5 in that example, and while typing this up i figured out
> how to get it, but I'm still not sure what _was_ happening)
>
> I'm trying
>
> >>>> a=[]
> >>> row=[ [] for n in range(0,10) ]
> >>> a.extend(row[:])
> >>> a
>
> [[], [], [], [], [], [], [], [], [], []]>>> a[0].extend(row[:])
> >>> a
>
> [[[...], [], [], [], [], [], [], [], [], []], [], [], [], [], [], [], [],
> [], []]
>
> why isnt that last a
>
> [[[...]],[],[],[],[],[],[],[],[],[]]
>
> Puzzled :)

I don't see why you should get either.

Especially considering this behaviour:

>>> a=[]
>>> row=[ [] for n in range(0,10) ]
>>> a.extend(row[:])
>>> a
[[], [], [], [], [], [], [], [], [], []]
>>> a[0].extend(row[:])
>>> a
[[[...], [], [], [], [], [], [], [], [], []], [], [], [], [], [], [],
[], [], []]

>>> a[0][0][0][0][0][0][0][0][0][0][0][0][0][0]
[[...], [], [], [], [], [], [], [], [], []]

>>> a=[]
>>> row=[ [] for n in range(0,10) ]
>>> a.extend(row[:])
>>> a
[[], [], [], [], [], [], [], [], [], []]

Bug in IDLE?

>
> Matt.
> --
>
> This message and any attachments (the "message") is
> intended solely for the addressees and is confidential.
> If you receive this message in error, please delete it and
> immediately notify the sender. Any use not in accord with
> its purpose, any dissemination or disclosure, either whole
> or partial, is prohibited except formal approval. The internet
> can not guarantee the integrity of this message.
> BNP PARIBAS (and its subsidiaries) shall (will) not
> therefore be liable for the message if modified.
> Do not print this message unless it is necessary,
> consider the environment.
>
>                 ---------------------------------------------
>
> Ce message et toutes les pieces jointes (ci-apres le
> "message") sont etablis a l'intention exclusive de ses
> destinataires et sont confidentiels. Si vous recevez ce
> message par erreur, merci de le detruire et d'en avertir
> immediatement l'expediteur. Toute utilisation de ce
> message non conforme a sa destination, toute diffusion
> ou toute publication, totale ou partielle, est interdite, sauf
> autorisation expresse. L'internet ne permettant pas
> d'assurer l'integrite de ce message, BNP PARIBAS (et ses
> filiales) decline(nt) toute responsabilite au titre de ce
> message, dans l'hypothese ou il aurait ete modifie.
> N'imprimez ce message que si necessaire,
> pensez a l'environnement.