CREATE FUNCTION return_str_arr()
  RETURNS varchar[]
AS $$
return "hello"
$$ LANGUAGE plpython3u;

SELECT return_str_arr();
 return_str_arr
----------------
 {h,e,l,l,o}
(1 row)
</programlisting>
  </para>
  </sect2>

  <sect2 id="plpython-data-composite-types">
   <title>Composite Types</title>
  <para>
   Composite-type arguments are passed to the function as Python mappings. The
   element names of the mapping are the attribute names of the composite type.
   If an attribute in the passed row has the null value, it has the value
   <symbol>None</symbol> in the mapping. Here is an example:

<programlisting>
CREATE TABLE employee (
  name text,
  salary integer,
  age integer
);

CREATE FUNCTION overpaid (e employee)
  RETURNS boolean
AS $$
  if e["salary"] &gt; 200000:
    return True
  if (e["age"] &lt; 30) and (e["salary"] &gt; 100000):
    return True
  return False
$$ LANGUAGE plpython3u;
</programlisting>
  </para>

  <para>
   There are multiple ways to return row or composite types from a Python
   function. The following examples assume we have:

<programlisting>
CREATE TYPE named_value AS (
  name   text,
  value  integer
);
</programlisting>

   A composite result can be returned as a:

   <variablelist>
    <varlistentry>
     <term>Sequence type (a tuple or list, but not a set because
     it is not indexable)</term>
     <listitem>
      <para>
       Returned sequence objects must have the same number of items as the
       composite result type has fields. The item with index 0 is assigned to
       the first field of the composite type, 1 to the second and so on. For
       example:

<programlisting>
CREATE FUNCTION make_pair (name text, value integer)
  RETURNS named_value
AS $$
  return ( name, value )
  # or alternatively, as list: return [ name, value ]
$$ LANGUAGE plpython3u;
</programlisting>

       To return an SQL null for any column, insert <symbol>None</symbol> at
       the corresponding position.
      </para>
      <para>
       When an array of composite types is returned, it cannot be returned as a list,
       because it is ambiguous whether the Python list represents a composite type,
       or another array dimension.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>Mapping (dictionary)</term>
     <listitem>
      <para>
       The value for each result type column is retrieved from the mapping
       with the column name as key. Example:

<programlisting>
CREATE FUNCTION make_pair (name text, value integer)
  RETURNS named_value
AS $$
  return { "name": name, "value": value }
$$ LANGUAGE plpython3u;
</programlisting>

       Any extra dictionary key/value pairs are ignored. Missing keys are
       treated as errors.
       To return an SQL null value for any column, insert
       <symbol>None</symbol> with the corresponding column name as the key.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>Object (any object providing method <literal>__getattr__</literal>)</term>
     <listitem>
      <para>
       This works the same as a mapping.
       Example:

<programlisting>
CREATE FUNCTION make_pair (name text, value integer)
  RETURNS named_value
AS $$
  class named_value:
    def __init__ (self, n, v):
      self.name = n
      self.value = v
  return named_value(name, value)

  # or simply
  class nv: pass
  nv.name = name
  nv.value = value
  return nv
$$ LANGUAGE plpython3u;
</programlisting>
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>

   <para>
    Functions with <literal>OUT</literal> parameters are also supported.  For example:
<programlisting>
CREATE FUNCTION multiout_simple(OUT i integer, OUT j integer) AS $$
return (1, 2)
$$ LANGUAGE plpython3u;

SELECT * FROM multiout_simple();
</programlisting>
   </para>

   <para>
    Output parameters of procedures are passed back the same way.  For example:
<programlisting>
CREATE PROCEDURE python_triple(INOUT a integer, INOUT b integer) AS