[Tutor] Is there any logic in this?

[Righard/Riku van Roy]

If you copy a list into another variable, and then change the second
one, the first gets changed aswell, for example:

>>> a = [10, 40, 30, 20]
>>> b = a
>>> b.sort()
>>> a
[10, 20, 30, 40]
>>> b
[10, 20, 30, 40]
 
or:

>>> a = [10, 40, 30, 20]
>>> b = a
>>> b[0] = 99
>>> a
[99, 40, 30, 20]
>>> b
[99, 40, 30, 20]

this happens with dictionary's too, but not with intergers, it is not
that this is a problem because I can just use...

>>> b = a[:]

...but I wonder if there is any logic behind this, I cannot find a
practical use for it, just problems.

thx, Righard