Convert Pandas dataframe to csv string

The simplest way is just to not input any filename, in this case a string is returned:

>>> df = pd.DataFrame({'A' : [0, 1], 'B' : [1, 6]})
>>> df.to_csv()
',A,B\n0,0,1\n1,1,6\n'

In [10]: df = pd.DataFrame({'A' : [0, 1], 'B' : [1, 6]})

In [11]: import io

In [12]: s = io.StringIO()

In [13]: df.to_csv(s)

In [14]: s.getvalue()
Out[14]: ',A,B\n0,0,1\n1,1,6\n'