Generating list sequence with a custom step in Python

Question

Okay, i'm really stuck with that one-liner.

Yet tried to accomplish my task with zip and map, but none of it worked i want. So my question is: can i generate a list with a custom step like this?

>>wicked cool code snippet
>>[101, 105, 109, 115, 121]

The idea behind this is that i have the start of a sequence X equal to 101. Then i add 4, then again adding 4. Then i add 6 to the previous result and again i add 6.

I believe it should look like this mathematically speaking:

An = A1+4d,A2+4d,A3+6d, A4+6d.

UPD

Ok, let me make it more clear.

range(101, 120, 3) <-Classical arithmetical progression

[101, 104, 107, 110, 113, 116, 119] < - The output

What i need is a combination of two of them. Like add +4 to each element n-times, then add +6 to the last element of add 4 sequence n-times.

Hope, it's clearer now.

It's hard to answer your question in it's current form, because there is no obvious way the sequence should continue (should A5 and A6 use +8 instead of +6?) - if it continues at all. — orlp
– orlp, Commented Mar 18, 2013 at 9:14
Maybe do some functional operation on 101 and [4, 4, 6, 6]? I want to say fold using addition, except that goes all the way, so you'd have to do it in a range or something. Slightly beyond my brain ATM. — Patashu
– Patashu, Commented Mar 18, 2013 at 9:14
its not clear. what does 4 or 6 signify? length of the previous word? — Srikar Appalaraju
– Srikar Appalaraju, Commented Mar 18, 2013 at 9:15
You can't do that with just zip and map, some sort of accumulator must be involved. — Dmytro Sirenko
– Dmytro Sirenko, Commented Mar 18, 2013 at 9:22

Fredrik Pihl · Accepted Answer · 2013-03-18 09:24:53Z

2

A bit hardcoded:

In [42]: step=[0,3,6,11,16]

In [43]: [i+step[n] for n, i in enumerate(range(101, 106))]
Out[43]: [101, 105, 109, 115, 121]

answered Mar 18, 2013 at 9:24

Fredrik Pihl

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Alex Reynolds · Accepted Answer · 2013-03-18 09:29:17Z

1

Not sure if this is a wicked cool code snippet, but it returns your answer with one line of code:

 >>> map(lambda x: x+100 if x == 1 else (x+103 if x == 2 else (x+106 if x == 3 else (x+111 if x == 4 else x+116))), range(1,6))
 [101, 105, 109, 115, 121]

answered Mar 18, 2013 at 9:29

Alex Reynolds

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Dmytro Sirenko · Accepted Answer · 2013-03-18 09:36:44Z

1

This works for me:

>>> reduce(lambda acc, i: acc + [acc[-1] + i], [4,4,6,6], [101])
[101, 105, 109, 115, 121]

Unfortunately, it is not exactly what you've asked for and I am afraid it just can't be done with map and zip alone, because these operations do not involve any kind of accumulator.

edited Mar 18, 2013 at 9:36

answered Mar 18, 2013 at 9:29

Dmytro Sirenko

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