I was playing around in python. I used the following code in IDLE:
p = [1, 2]
p[1:1] = [p]
print p
The output was:
[1, [...], 2]
What is this […]? Interestingly I could now use this as a list of list of list up to infinity i.e.
p[1][1][1]....
I could write the above as long as I wanted and it would still work.
EDIT:
How is it represented in memory?
What's its use? Examples of some cases where it is useful would be helpful.
Any link to official documentation would be really useful.
解决方案
It means that you created an infinite list nested inside itself, which can not be printed. p contains p which contains p ... and so on. The [...] notation is a way to let you know this, and to inform that it can't be represented! Take a look at @6502's answer to see a nice picture showing what's happening.
Now, regarding the three new items after your edit:
This answer seems to cover it
Ignacio's link describes some possible uses
This is more a topic of data structure design than programming languages, so it's unlikely that any reference is found in Python's official documentation