Is this the correct behavior?

>>> l=[['']*2]*3
>>> b=[['', ''], ['', ''], ['', '']]
>>> l == b
True
>>> l[0][1]='A'
>>> b[0][1]='A'
>>> l == b
False
>>> l
[['', 'A'], ['', 'A'], ['', 'A']]
>>> b
[['', 'A'], ['', ''], ['', '']]

Your list `l` actually holds only one list, except three times. When you change it, it's reflected in all the lists. It's the equivalent of the following:

>>> x=['', '']
>>> l=[x, x, x]

Makes a bit more sense this way? Either way, yes, this is intentional behaviour.

Another way to fix this would be the following:

>>> l=[[''] * 2 for _ in range(3)]
>>> l
[['', ''], ['', ''], ['', '']]
>>> l[0][1] = "A"
>>> l
[['', 'A'], ['', ''], ['', '']]

The * operator on lists doesn't create new elements, it only adds new references to them. A list comprehension will evaluate the expression each time, while repetition (the * operator) will only evaluate it once.

Thanks for the quick response.
It makes sense to me. I misunderstood the * operator.