deephaven.jcompat

This module provides Java compatibility support including convenience functions to create some widely used Java data structures from corresponding Python ones in order to be able to call Java methods.

class AutoCloseable(j_auto_closeable)

Bases: JObjectWrapper

A context manager wrapper to allow Java AutoCloseable to be used in with statements.

When constructing a new instance, the Java AutoCloseable must not be closed.

j_object_type

alias of AutoCloseable

dh_null_to_nan(np_array, type_promotion=False)

Converts Deephaven primitive null values in the given numpy array to np.nan. No conversion is performed on non-primitive types.

Note, the input numpy array is modified in place if it is of a float or double type. If that’s not a desired behavior, pass a copy of the array instead. For input arrays of other types, a new array is always returned.

Parameters:

• np_array (np.ndarray) – The numpy array to convert

• type_promotion (bool) – When False, integer, boolean, or character arrays will cause an exception to be raised. When True, integer, boolean, or character arrays are converted to new np.float64 arrays and Deephaven null values in them are converted to np.nan. Numpy arrays of float or double types are not affected by this flag and Deephaven nulls will always be converted to np.nan in place. Defaults to False.

Returns:

The numpy array with Deephaven nulls converted to np.nan.

Return type:

np.ndarray

Raises:

DHError –

is_java_type(obj)

Returns True if the object is originated in Java.

Return type:

bool

j_array_list(values=None)

Creates a Java ArrayList instance from an iterable.

Return type:

JType

j_binary_operator(func, dtype)

Constructs a Java ‘Function<PyObject, PyObject, Object>’ implementation from a Python callable or an object with an ‘apply’ method that accepts a single argument.

Parameters:

• func (Callable) – a Python callable or an object with an ‘apply’ method that accepts two arguments

• dtype (DType) – the return type of ‘func’

Return type:

JType

Returns:

io.deephaven.integrations.python.PythonFunction instance

j_function(func, dtype)

Constructs a Java ‘Function<PyObject, Object>’ implementation from a Python callable or an object with an ‘apply’ method that accepts a single argument.

Parameters:

• func (Callable) – a Python callable or an object with an ‘apply’ method that accepts a single argument

• dtype (DType) – the return type of ‘func’

Return type:

JType

Returns:

io.deephaven.integrations.python.PythonFunction instance

j_hashmap(d=None)

Creates a Java HashMap from a dict.

Return type:

JType

j_hashset(s=None)

Creates a Java HashSet from a set.

Return type:

JType

j_lambda(func, lambda_jtype, return_dtype=None)

Wraps a Python Callable as a Java “lambda” type.

Java lambda types must contain a single abstract method.

Parameters:

• func (Callable) – Any Python Callable or object with an ‘apply’ method that accepts the same arguments (number and type) the target Java lambda type

• lambda_jtype (jpy.JType) – The Java lambda interface to wrap the provided callable in

• return_dtype (DType) – The expected return type if conversion should be applied. None (the default) does not attempt to convert the return value and returns a Java Object.

j_list_to_list(jlist)

Converts a java list to a python list.

Return type:

List[Any]

j_map_to_dict(m)

Converts a java map to a python dictionary.

Return type:

Dict[Any, Any]

j_properties(d=None)

Creates a Java Properties from a dict.

Return type:

JType

j_runnable(callable)

Constructs a Java ‘Runnable’ implementation from a Python callable that doesn’t take any arguments and returns None.

Parameters:

callable (Callable[[], None]) – a Python callable that doesn’t take any arguments and returns None

Return type:

JType

Returns:

io.deephaven.integrations.python.PythonRunnable instance

j_table_definition(table_definition)

Deprecated for removal next release, prefer TableDefinition. Produce a Deephaven TableDefinition from user input.

Parameters:

table_definition (Optional[TableDefinitionLike]) – the table definition as a dictionary of column names and their corresponding data types or a list of Column objects

Return type:

Optional[JType]

Returns:

a Deephaven TableDefinition object or None if the input is None

Raises:

DHError –

j_unary_operator(func, dtype)

Constructs a Java ‘Function<PyObject, Object>’ implementation from a Python callable or an object with an ‘apply’ method that accepts a single argument.

Parameters:

• func (Callable) – a Python callable or an object with an ‘apply’ method that accepts a single argument

• dtype (DType) – the return type of ‘func’

Return type:

JType

Returns:

io.deephaven.integrations.python.PythonFunction instance

to_sequence(v=None, wrapped=False)

A convenience function to create a sequence of wrapped or unwrapped object from either one or a sequence of input values to help JPY find the matching Java overloaded method to call.

This also enables a function to provide parameters that can accept both singular and plural values of the same type for the convenience of the users, e.g. both x= “abc” and x = [“abc”] are valid arguments.

Parameters:

• v (Union[T, Sequence[T]], optional) – the input value(s) to be converted to a sequence

• wrapped (bool, optional) – if True, the input value(s) will remain wrapped in a JPy object; otherwise, the input value(s) will be unwrapped. Defaults to False.

Returns:

a sequence of wrapped or unwrapped objects

Return type:

Sequence[Union[T, jpy.JType]]