In Python, you can use copy or deepcopy (from module copy) to pass a copy of an object rather than the object itself.

import copy

a = [1,2,3]
b = a
b[2] = 99 # now a[2] = 99 too

a = [1,2,3]
b = copy.copy(a)
b[2] = 99 # now a[2] is unchanged

To sum up, you could pass your lists to the dictionary as:

dictionary[key] = copy.copy(value_list) # or use copy.deepcopy

For nested structures, use copy.deepcopy instead of copy.copy so that you create a copy of all the nested levels.

Cheers

Here's an ipython session that illuminates why you're seeing what you're seeing.

In [1]: d = {}

In [2]: alist = range(4)

In [3]: d['bad'] = alist

In [4]: d['ok'] = alist[:]

In [5]: alist.append("EXTRA")

In [6]: d
Out[6]: {'bad': [0, 1, 2, 3, 'EXTRA'], 'ok': [0, 1, 2, 3]}

Note that alist[:] makes a copy so it is not affected by the subsequent append. You can also use copy.copy() for more rigor as suggested by @Eric.