Python lacks dynamic unpacking. Example: You want to unpack a list, let's say coordinates, but don't know whether it contains 3 items or just 2.

x, y, z = [1,2,3] works only if len([x,y,z]) == len([1,2,3]).

x, y, z = [1,2] results in an error. You could add try and except blocks but that could be complicated.

The best option is z being None, as you can simply check using if n is None without any excessive try/except.

So expected result:

>>> x, y, z = unpack([1,2])
>>> print(x)
1
>>> print(y)
2
>>> print(z)
None

My code [permalink]

def unpack(num, list):
    return_arr = [None] * num
    for i,elem in enumerate(list):
        return_arr[i] = elem
        if i+1 == num:
            return return_arr
    return return_arr

And usage examples:

a,b,c,d = unpack(4, [1,2,3])
print(a),
print(b),
print(c),
print(d),
print("\n")

e,f,g = unpack(3, [1,2,3])
print(e),
print(f),
print(g)

resulting in

1 2 3 None 

1 2 3

You basically have to specify the amount of variables you're unpacking the list to, since the function can't know that.