[Tutor] dealing with lists

[Alan Gauld]

On 23/02/2022 20:11, marcus.luetolf at bluewin.ch wrote:

> I'd like to create  5 lists, each containing 4 sublists : f1, f2, f3, f4,
> f5, a total of 20 sublists.

That's not what your code below does. It only creates the 4 sublists.
But then it throws them away and creates another 4 and starts again.

> I have a list (named all_letters) contaning 16 characters a, b, c, ...p.
> 
> I  would liketo  distribute all 16 characters to the 4 sublists 5 times in 5
> iterations respectivly  so that as a condition a pair of characters, 
> p.e. ['a', 'b', .]  or ['a', 'c'.] or ['n', 'p' .] can appear only once 
> in all 20 sublists.

You can probably use some of the python modules to do that
for you as a set of combinations or permutations or whatever
you actually want.

> To find the sublists fullfilling this condition I designed the following
> code with the intention to change the indices
> defined by the variables n and p til the condition is met :
> 
>  
> 
> all_letters = list('abcdefghijklmnop')
> 
> f1 = []
> 
> f2 = []
> 
> f3 = []
> 
> f4 = []

Why not just define these at the top of the function
so you only have to do it once?

> n = 0
> p = 1
> for dummy_i in range(5):  
>     copy_all_letters = all_letters[:]
>     lst = 16*copy_all_letters
> 
>     f1.append(lst[n+0])
>     f1.append(lst[n+p])
>     f1.append(lst[n+2*p])
>     f1.append(lst[n+3*p])
>     f1.sort()

You could do that all in one line:

f1 = sorted([ lst[n],lst[n+p],lst[n+2*p], lst[n+3*p] ])

...
>     f2.sort()
> 
...
>     f3.sort()
...>     f4.sort()

>     print('f1: ', f1)
>     print('f2: ', f2)
>     print('f3: ', f3)
>     print('f4: ', f4)
> 
>     n += 4
>     p += 1
> 
>     f1 = []
> 
>     f2 = []
> 
>     f3 = []
> 
>     f4 = []
> 
>     f5 = []

Where did f5 come from? You only build 4 lists?
And you've now thrown them away and are staring
from scratch with new indices.

> But I'm unable to define the condition mentioned 
> above and asking for your help.

I don't understand that comment. Can you be more
specific about what you expect and what you get?


-- 
Alan G
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