Class _FunctionGenerator

lib/sqlalchemy/sql/functions.py:861–1275

Generate SQL function expressions. :data:`.func` is a special object instance which generates SQL functions based on name-based attributes, e.g.: .. sourcecode:: pycon+sql >>> print(func.count(1)) {printsql}count(:param_1) The returned object is an instance of :cl

class _FunctionGenerator:
    """Generate SQL function expressions.

    :data:`.func` is a special object instance which generates SQL
    functions based on name-based attributes, e.g.:

    .. sourcecode:: pycon+sql

        >>> print(func.count(1))
        {printsql}count(:param_1)

    The returned object is an instance of :class:`.Function`, and  is a
    column-oriented SQL element like any other, and is used in that way:

    .. sourcecode:: pycon+sql

        >>> print(select(func.count(table.c.id)))
        {printsql}SELECT count(sometable.id) FROM sometable

    Any name can be given to :data:`.func`. If the function name is unknown to
    SQLAlchemy, it will be rendered exactly as is. For common SQL functions
    which SQLAlchemy is aware of, the name may be interpreted as a *generic
    function* which will be compiled appropriately to the target database:

    .. sourcecode:: pycon+sql

        >>> print(func.current_timestamp())
        {printsql}CURRENT_TIMESTAMP

    To call functions which are present in dot-separated packages,
    specify them in the same manner:

    .. sourcecode:: pycon+sql

        >>> print(func.stats.yield_curve(5, 10))
        {printsql}stats.yield_curve(:yield_curve_1, :yield_curve_2)

    SQLAlchemy can be made aware of the return type of functions to enable
    type-specific lexical and result-based behavior. For example, to ensure
    that a string-based function returns a Unicode value and is similarly
    treated as a string in expressions, specify
    :class:`~sqlalchemy.types.Unicode` as the type:

    .. sourcecode:: pycon+sql

        >>> print(
        ...     func.my_string("hi", type_=Unicode)
        ...     + " "
        ...     + func.my_string("there", type_=Unicode)
        ... )
        {printsql}my_string(:my_string_1) || :my_string_2 || my_string(:my_string_3)

    The object returned by a :data:`.func` call is usually an instance of
    :class:`.Function`.
    This object meets the "column" interface, including comparison and labeling
    functions.  The object can also be passed the :meth:`~.Connectable.execute`
    method of a :class:`_engine.Connection` or :class:`_engine.Engine`,
    where it will be