lidavidm commented on code in PR #12590:
URL: https://github.com/apache/arrow/pull/12590#discussion_r841960296
##########
python/pyarrow/_compute.pyx:
##########
@@ -2251,3 +2325,148 @@ cdef CExpression _bind(Expression filter, Schema
schema) except *:
return GetResultValue(filter.unwrap().Bind(
deref(pyarrow_unwrap_schema(schema).get())))
+
+
+cdef CFunctionDoc _make_function_doc(dict func_doc):
+ """
+ Helper function to generate the FunctionDoc
+ """
+ cdef:
+ CFunctionDoc f_doc
+ vector[c_string] c_arg_names
+ c_bool c_options_required
+
+ f_doc.summary = tobytes(func_doc["summary"])
+ f_doc.description = tobytes(func_doc["description"])
+ for arg_name in func_doc["arg_names"]:
+ c_arg_names.push_back(tobytes(arg_name))
+ f_doc.arg_names = c_arg_names
+ # UDFOptions integration:
+ # TODO: https://issues.apache.org/jira/browse/ARROW-16041
+ f_doc.options_class = tobytes("None")
+ c_options_required = False
+ f_doc.options_required = c_options_required
+ return f_doc
+
+
+def register_function(func_name, num_args, function_doc, in_types,
+ out_type, callback):
+ """
+ Register a user-defined-function.
+
+ Parameters
+ ----------
+
+ func_name : str
+ function name
+ num_args : int
+ number of arguments in the function
+ function_doc : dict
+ a dictionary object with keys "summary" (str),
+ "description" (str), and "arg_names" (list of str).
+ in_types : List[InputType]
+ list of InputType objects which defines the input
+ types for the function
+ out_type : DataType
+ output type of the function
+ callback : callable
+ user defined function
+ function includes arguments equal to the number
+ of input_types defined. The return type of the
+ function is of the type defined as output_type.
+ The output should be an Array, Scalar, ChunkedArray,
+ Table, or RecordBatch based on the out_type.
+
+ Example
+ -------
+
+ >>> from pyarrow import compute as pc
+ >>> from pyarrow.compute import register_function
+ >>> from pyarrow.compute import InputType
+ >>>
+ >>> func_doc = {}
+ >>> func_doc["summary"] = "simple udf"
+ >>> func_doc["description"] = "add a constant to a scalar"
+ >>> func_doc["arg_names"] = ["x"]
+ >>>
+ >>> def add_constant(array):
+ ... return pc.call_function("add", [array, 1])
+ ...
+ >>>
+ >>> func_name = "py_add_func"
+ >>> arity = 1
+ >>> in_types = [InputType.array(pa.int64())]
+ >>> out_type = pa.int64()
+ >>> register_function(func_name, arity, func_doc,
+ ... in_types, out_type, add_constant)
+ >>>
+ >>> func = pc.get_function(func_name)
+ >>> func.name
+ 'py_add_func'
+ >>> ans = pc.call_function(func_name, [pa.array([20])])
+ >>> ans
+ <pyarrow.lib.Int64Array object at 0x10c22e700>
+ [
+ 21
+ ]
+ """
+ cdef:
+ c_string c_func_name
+ CArity c_arity
+ CFunctionDoc c_func_doc
+ CInputType in_tmp
+ vector[CInputType] c_in_types
+ PyObject* c_callback
+ shared_ptr[CDataType] c_type
+ COutputType* c_out_type
+ CScalarUdfBuilder* c_sc_builder
+ CStatus st
+ CScalarUdfOptions* c_options
+ object obj
+
+
+ c_func_name = tobytes(func_name)
+
+ if num_args and isinstance(num_args, int):
+ if not(num_args >= 0):
+ raise ValueError("number of arguments must be >= 0")
Review Comment:
```suggestion
if num_args <= 0:
raise ValueError("number of arguments must be >= 0")
```
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