One assignment method in mixed type dataframe not working
I tried several ways of assigning values in a mixed type dataframe and it seems that one of them is not working. I am not sure if it is supposed to do so:

from pandas import DataFrame
df = DataFrame({'A':[:'aaa','bbb','ccc'],'B':[1,2,3]})
# this works, value is changed

df.ix[0,'A'] = 11
# this works, value is changed

df['A'][0] = 111
# this does not work, value is not changed

df.ix[0]['A'] = 1111
