indexからcolumnへ、columnからindexへ ref: https://qiita.com/kyoro1/items/56c1606e0218fbfae32d

file0.txt

import pandas as pd

df = \
pd.DataFrame({ 'date' : ['2017-12-14','2017-12-15','2017-12-16'],
               'symbol' : ["A","B","C"],
               'number' : [1,2,3]})

file1.txt

>>> df
         date  number symbol
0  2017-12-14       1      A
1  2017-12-15       2      B
2  2017-12-16       3      C

>>> df.index
RangeIndex(start=0, stop=3, step=1)

>>> df.columns
Index([u'date', u'number', u'symbol'], dtype='object')

file2.txt

## "date"カラムの内容をindexに指定
df1 = df.set_index("date")

>>> df1
            number symbol
date
2017-12-14       1      A
2017-12-15       2      B
2017-12-16       3      C

>>> df1.index
Index([u'2017-12-14', u'2017-12-15', u'2017-12-16'], dtype='object', name=u'date')

>>> df1.columns
Index([u'number', u'symbol'], dtype='object')

file3.txt

df2 = df1.reset_index()

>>> df2
         date  number symbol
0  2017-12-14       1      A
1  2017-12-15       2      B
2  2017-12-16       3      C

>>> df2.index
RangeIndex(start=0, stop=3, step=1)

>>> df2.columns
Index([u'date', u'number', u'symbol'], dtype='object')