Python dictionnaire vs liste

cat = dict()
cat['env'] = dict()
cat['env']['path'] = 'c:\program..'
cat['bases'] = list()
cat['database'] = dict()
cat['database']['name'] = "first"
cat['database']['path'] = 'here'
cat['bases'].append(cat['database'])
print cat['bases']
[{'path': 'here', 'name': 'first'}]
cat['database']['name'] = ""
cat['database']['path'] = ""
print cat['bases']
[{'path': '', 'name': ''}]