[Chicago] A list comprehension???

[Lewit, Douglas]

I've been playing with this, and I think I've got it!!!

Here's what I have:

[sum([2*k for k in range(i)]) for i in range(1, 11)]

I started with sum(2*k for k in range(10)) and noticed that gave me 90, and
then when you substitute range(9) then you get 72, etc.  So.... I think I
got it!  Am I a Python genius or what?!   ;-)

I'm guessing that list comprehensions, set comprehensions, generator
comprehensions, etc, etc are used a lot in functional programming.  I have
this ebook on functional programming in Python.  Some of it is really cool,
and some of it is almost like rocket science to me.... but I'm learning.

On Mon, May 4, 2015 at 6:58 PM, Adam Forsyth <adam at adamforsyth.net> wrote:

> There is a different algorithm, one that doesn't refer to the previous
> item in the list, that produces those numbers. Think about what kind of
> algebraic function generally produces a series of numbers that get farther
> and farther apart.
>
> On Mon, May 4, 2015 at 6:39 PM, Lewit, Douglas <d-lewit at neiu.edu> wrote:
>
>> Hi there,
>>
>> I'm reading this book, "Data Structures & Algorithms in Python" by
>> Goodrich, Tamassia, and Goldwasser.  A pretty good book, it really does
>> into detail about the Python language with various examples.
>>
>> Anyhow, one of the exercises is as follows:
>>
>> Demonstrate how to use Python's list comprehension syntax to produce the
>> list:
>> [0, 2, 6, 12, 20, 30, 42, 56, 72, 90].
>>
>> I'm struggling with this!
>>
>> The best I can do is the following:
>>
>> A = [0]
>> i = 2
>> while i <= 18:
>>     A.append(A[-1] + i)
>>      i+= 2
>>
>> print(A)
>>
>> Well it does work!  BUT it's not a list comprehension!
>>
>> Any suggestions?
>>
>> Thanks,
>>
>> Douglas.
>>
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>
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