Using 0.13.1 (gohlke binaries, Win64, using numpy 1.8):
When using .loc, when passing unsorted labels, pandas doesn't assign the values in the designed labels' locations. Example:
df = pandas.DataFrame(index=[3, 5, 4], columns=['A'])
df.loc[[4, 3, 5], 'A'] = [1, 2, 3]
Result is:
One would have expected: