Understand list comprehension and draw

[PUP280]

Hello,

I'm a beginner and I try a lot of things with list comprehension to understand it. Considering that, I don't understand some things.

First, how can I do only one draw by combination ? I explain, if I wrote this :

mylist = [1,2,3,4]
[(x,y,z) for x in mylist for y in mylist for z in mylist if x != y if y != z if x != z]

I got this :

Output:
[(1, 2, 3), (1, 2, 4), (1, 3, 2), (1, 3, 4), (1, 4, 2), (1, 4, 3), (2, 1, 3), (2, 1, 4), (2, 3, 1), (2, 3, 4), (2, 4, 1), (2, 4, 3), (3, 1, 2), (3, 1, 4), (3, 2, 1), (3, 2, 4), (3, 4, 1), (3, 4, 2), (4, 1, 2), (4, 1, 3), (4, 2, 1), (4, 2, 3), (4, 3, 1), (4, 3, 2)]

But (1,2,3), (1,3,2), (2,1,3), ... are the same combination in my example.
How can I write my code to have only one draw with these three different numbers ?

I've searched a solution with itertool but I've found nothing. Maybe dropwhile but I have not succeed with.

Otherwise, if I write this :

[(x,y) for x in list(range(10)) for y in list(range(20)]

How can I manage it to have all combinations except if x and y are between 0 and 4 ? In other words, if x is in [0:5], y can not.

I’ve thought about :

[(x,y) for x in list(range(10)) for y in list(range(20)) if x in [0:5] then not y]

But I idn’t find how can I put a ‘’then’’ in a list comprehension. Is it possible ?

I have the same doubt with pass, continue and break.

Rather than do without understand, is there a website where I can find tutorials about list comprehension ? I did not find it on Python documentations, but maybe I'm wrong.