import numpy as np
import pandas as pd

dtype = [('Col1','int32'), ('Col2','float32'), ('Col3','float32')]
values = np.zeros(20, dtype=dtype)
index = ['Row'+str(i) for i in range(1, len(values)+1)]

df = pd.DataFrame(values, index=index)
print(df)

       Col1  Col2  Col3
Row1      0   0.0   0.0
Row2      0   0.0   0.0
Row3      0   0.0   0.0
Row4      0   0.0   0.0
Row5      0   0.0   0.0
Row6      0   0.0   0.0
Row7      0   0.0   0.0
Row8      0   0.0   0.0
Row9      0   0.0   0.0
Row10     0   0.0   0.0
Row11     0   0.0   0.0
Row12     0   0.0   0.0
Row13     0   0.0   0.0
Row14     0   0.0   0.0
Row15     0   0.0   0.0
Row16     0   0.0   0.0
Row17     0   0.0   0.0
Row18     0   0.0   0.0
Row19     0   0.0   0.0
Row20     0   0.0   0.0