def test_write_csv_operator(self,duckdb_cursor):
conn = duckdb.connect()
df_rel = get_relation(conn)
temp_file_name = os.path.join(tempfile.mkdtemp(), next(tempfile._get_candidate_names()))
df_rel.write_csv(temp_file_name)
csv_rel = duckdb.from_csv_auto(temp_file_name)
assert df_rel.execute().fetchall() == csv_rel.execute().fetchall()
def test_from_csv(self, duckdb_cursor):
temp_file_name = os.path.join(tempfile.mkdtemp(), next(tempfile._get_candidate_names()))
conn = duckdb.connect()
conn.execute("create table t (a integer)")
conn.execute("insert into t values (1)")
test_df = pd.DataFrame.from_dict({"i":[1, 2, 3, 4]})
test_df.to_csv(temp_file_name, index=False)
rel = duckdb.from_csv_auto(temp_file_name, conn)
assert rel.query('t_2','select count(*) from t inner join t_2 on (a = i)').fetchall()[0] == (1,)
def test_csv_auto(self, duckdb_cursor):
conn = duckdb.connect()
df_rel = get_relation(conn)
temp_file_name = os.path.join(tempfile.mkdtemp(), next(tempfile._get_candidate_names()))
test_df = pd.DataFrame.from_dict({"i":[1, 2, 3, 4], "j":["one", "two", "three", "four"]})
test_df.to_csv(temp_file_name, index=False)
# now create a relation from it
csv_rel = duckdb.from_csv_auto(temp_file_name)
assert df_rel.execute().fetchall() == csv_rel.execute().fetchall()
def test_df_write_csv(self, duckdb_cursor):
test_df = pd.DataFrame.from_dict({
"i": [1, 2, 3, 4],
"j": ["one", "two", "three", "four"]
})
temp_file_name = os.path.join(tempfile.mkdtemp(),
next(tempfile._get_candidate_names()))
duckdb.write_csv(test_df, temp_file_name)
csv_rel = duckdb.from_csv_auto(temp_file_name)
assert csv_rel.execute().fetchall() == [(1, 'one'), (2, 'two'),
(3, 'three'), (4, 'four')]
print(rel)
# alternative shorthand, use a built-in default connection to create a relation from a pandas data frame
rel = duckdb.df(test_df)
print(rel)
# create a relation from a CSV file
# first create a CSV file from our pandas example
import tempfile, os
temp_file_name = os.path.join(tempfile.mkdtemp(),
next(tempfile._get_candidate_names()))
test_df.to_csv(temp_file_name, index=False)
# now create a relation from it
rel = duckdb.from_csv_auto(temp_file_name)
print(rel)
# create a relation from an existing table
rel = conn.table("test_table")
print(rel)
# a relation has an alias (like a table name)
print(rel.alias)
# we can change the alias, useful for (self)joins for example
rel2 = rel.set_alias('new_alias')
print(rel2.alias)
# we can inspect the type of a relation
print(rel.type)