import pandas as pd

df1 = pd.DataFrame(
   [[5, 2], [4, 1]],
   index=["One", "Two"],
   columns=["Rank", "Subjects"]
)

df2 = pd.DataFrame(
   [[15, 21], [41, 11]],
   index=["One", "Two"],
   columns=["Rank", "Subjects"]
)

print "DataFrame 1:\n", df1
print "DataFrame 2:\n", df2

with pd.ExcelWriter('output.xlsx') as writer:
df1.to_excel(writer, sheet_name='Sheet_name_1')
df2.to_excel(writer, sheet_name='Sheet_name_2')

DataFrame 1:

    Rank  Subjects
One    5     2
Two    4     1

DataFrame 2:

    Rank   Subjects
One   15     21
Two   41     11