Class BaseFormatter

IPython/core/formatters.py:287–564

A base formatter class that is configurable. This formatter should usually be used as the base class of all formatters. It is a traited :class:`Configurable` class and includes an extensible API for users to determine how their objects are formatted. The following logic is used to f

class BaseFormatter(Configurable):
    """A base formatter class that is configurable.

    This formatter should usually be used as the base class of all formatters.
    It is a traited :class:`Configurable` class and includes an extensible
    API for users to determine how their objects are formatted. The following
    logic is used to find a function to format an given object.

    1. The object is introspected to see if it has a method with the name
       :attr:`print_method`. If is does, that object is passed to that method
       for formatting.
    2. If no print method is found, three internal dictionaries are consulted
       to find print method: :attr:`singleton_printers`, :attr:`type_printers`
       and :attr:`deferred_printers`.

    Users should use these dictionaries to register functions that will be
    used to compute the format data for their objects (if those objects don't
    have the special print methods). The easiest way of using these
    dictionaries is through the :meth:`for_type` and :meth:`for_type_by_name`
    methods.

    If no function/callable is found to compute the format data, ``None`` is
    returned and this format type is not used.
    """

    format_type = Unicode('text/plain')
    _return_type = str

    enabled = Bool(True).tag(config=True)

    print_method = ObjectName('__repr__')

    # The singleton printers.
    # Maps the IDs of the builtin singleton objects to the format functions.
    singleton_printers = Dict().tag(config=True)

    # The type-specific printers.
    # Map type objects to the format functions.
    type_printers = Dict().tag(config=True)

    # The deferred-import type-specific printers.
    # Map (modulename, classname) pairs to the format functions.
    deferred_printers = Dict().tag(config=True)
    
    @catch_format_error
    def __call__(self, obj):
        """Compute the format for an object."""
        if self.enabled:
            # lookup registered printer
            try:
                printer = self.lookup(obj)
            except KeyError:
                pass
            else:
                return printer(obj)
            # Finally look for special method names
            method = get_real_method(obj, self.print_method)
            if method is not None: