Dataframes have a sort_index method which returns a copy by default. Pass inplace=True to operate in place.
import pandas as pd
df = pd.DataFrame([1, 2, 3, 4, 5], index=[100, 29, 234, 1, 150], columns=['A'])
df.sort_index(inplace=True)
print(df.to_string())
Gives me:
A
1 4
29 2
100 1
150 5
234 3