copy a list

In [8]: a = [1,2,3]

In [9]: b = a       # not a copy, b points to a

In [10]: id(a)
Out[10]: 3085175820L

In [11]: id(b)
Out[11]: 3085175820L

In [12]: b = a[:]    # [:] create a slice of the full list
In [13]: b = list(a) # alos creates a copy