# import necessary libraries
import pandas as pd
import numpy as np

# define your series and bins
series = pd.Series([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,\
                    12, 13, 14, 15, 16, 17, 18, 19, 20])

# use np.linspace method to create bin edges
bin_edges = np.linspace(series.min(), series.max(), num=10)
  
# bin series into 10 groups of equal sizes
bins = np.digitize(series, bin_edges, right=True)

# create new dataframe to display result in a better way
result_df = pd.DataFrame({'value': series, 'bin': bins})

# display result
print(result_df)