import duckdb
import pandas

# connect to an in-memory database
con = duckdb.connect()

input_df = pandas.DataFrame.from_dict({'i': [1, 2, 3, 4],
                                       'j': ["one", "two", "three", "four"]})

# create a DuckDB relation from a dataframe
rel = con.from_df(input_df)

# chain together relational operators (this is a lazy operation, so the operations are not yet executed)
# equivalent to: SELECT i, j, i*2 AS two_i FROM input_df WHERE i >= 2 ORDER BY i DESC LIMIT 2
transformed_rel = rel.filter('i >= 2').project('i, j, i*2 AS two_i').order('i DESC').limit(2)

# trigger execution by requesting .df() of the relation
# .df() could have been added to the end of the chain above - it was separated for clarity
output_df = transformed_rel.df()