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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
from typing import Union
duckdb.typing.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
print(duckdb.typing.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
print(duckdb.typing.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
from typing import Union
print(duckdb.typing.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.typing
:
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]