Questions on Using Python to Teach Data Structures and Algorithms

[Brendon Towle]

On 28 Sep 2006, at 12:45 PM, python-list-request at python.org wrote:

> From: "MonkeeSage" <MonkeeSage at gmail.com>
> Subject: Re: Questions on Using Python to Teach Data Structures and
> 	Algorithms
> To: python-list at python.org
>
> [snip]
> But Brendon's code also needs a correction: [a].extend(b) is wrong,
> because extend is in-place and returns None, and [a] is anonymous...it
> needs to be something like:
>
> def cons(a, b):
>   b.insert(0, a)
>   return b

Clearly, my Lisp is better than my Python; I stand corrected. (Brings  
back memories of the "Why don't destructive sequence operations  
return the sequence?" thread.)

I think I'd probably prefer:

def cons(a,b):
     res = [a]
     res.extend(b)
     return res

because cons is supposed to leave its second argument untouched.

B.

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Brendon Towle, PhD
Cognitive Scientist
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