Types API

The DuckDBPyType class represents a type instance of our data types.

Converting from Other Types

To make the API as easy to use as possible, we have added implicit conversions from existing type objects to a DuckDBPyType instance. This means that wherever a DuckDBPyType object is expected, it is also possible to provide any of the options listed below.

Python Built-Ins

The table below shows the mapping of Python Built-in types to DuckDB type.

Built-in types	DuckDB type
bool	BOOLEAN
bytearray	BLOB
bytes	BLOB
float	DOUBLE
int	BIGINT
str	VARCHAR

Numpy DTypes

The table below shows the mapping of Numpy DType to DuckDB type.

Type	DuckDB type
bool	BOOLEAN
float32	FLOAT
float64	DOUBLE
int16	SMALLINT
int32	INTEGER
int64	BIGINT
int8	TINYINT
uint16	USMALLINT
uint32	UINTEGER
uint64	UBIGINT
uint8	UTINYINT

Nested Types

list[child_type]

list type objects map to a LIST type of the child type. Which can also be arbitrarily nested.

import duckdb.sqltypes
from typing import Union

duckdb.sqltypes.DuckDBPyType(list[dict[Union[str, int], str]])

MAP(UNION(u1 VARCHAR, u2 BIGINT), VARCHAR)[]

dict[key_type, value_type]

dict type objects map to a MAP type of the key type and the value type.

import duckdb.sqltypes

print(duckdb.sqltypes.DuckDBPyType(dict[str, int]))

MAP(VARCHAR, BIGINT)

{'a': field_one, 'b': field_two, ..., 'n': field_n}

dict objects map to a STRUCT composed of the keys and values of the dict.

import duckdb.sqltypes

print(duckdb.sqltypes.DuckDBPyType({'a': str, 'b': int}))

STRUCT(a VARCHAR, b BIGINT)

Union[type_1, ... type_n]

typing.Union objects map to a UNION type of the provided types.

import duckdb.sqltypes
from typing import Union

print(duckdb.sqltypes.DuckDBPyType(Union[int, str, bool, bytearray]))

UNION(u1 BIGINT, u2 VARCHAR, u3 BOOLEAN, u4 BLOB)

Creation Functions

For the built-in types, you can use the constants defined in duckdb.sqltypes:

DuckDB type
BIGINT
BIT
BLOB
BOOLEAN
DATE
DOUBLE
FLOAT
HUGEINT
INTEGER
INTERVAL
SMALLINT
SQLNULL
TIME_TZ
TIME
TIMESTAMP_MS
TIMESTAMP_NS
TIMESTAMP_S
TIMESTAMP_TZ
TIMESTAMP
TINYINT
UBIGINT
UHUGEINT
UINTEGER
USMALLINT
UTINYINT
UUID
VARCHAR

For the complex types there are methods available on the DuckDBPyConnection object or the duckdb module. Anywhere a DuckDBPyType is accepted, we will also accept one of the type objects that can implicitly convert to a DuckDBPyType.

list_type | array_type

Parameters:

• child_type: DuckDBPyType

struct_type | row_type

Parameters:

• fields: Union[list[DuckDBPyType], dict[str, DuckDBPyType]]

map_type

Parameters:

• key_type: DuckDBPyType
• value_type: DuckDBPyType

decimal_type

Parameters:

• width: int
• scale: int

union_type

Parameters:

• members: Union[list[DuckDBPyType], dict[str, DuckDBPyType]]

string_type

Parameters:

• collation: Optional[str]