To change the attributes displayed by tab-completing your object, define a __dir__(self)
method for it. For more details, see the documentation of the built-in dir() function.
You can also customise key completions for your objects, e.g. pressing tab after obj["a
. To do so, define a method _ipython_key_completions_()
, which returns a list of objects which are possible keys in a subscript expression obj[key]
.
5.0 Custom key completions
The notebook and the Qt console can display richer representations of objects. To use this, you can define any of a number of _repr_*_()
methods. Note that these are surrounded by single, not double underscores.
Both the notebook and the Qt console can display svg
, png
and jpeg
representations. The notebook can also display html
, javascript
, markdown
and latex
. If the methods don't exist, or return None
, it falls back to a standard repr()
.
For example:
class Shout(object):
def __init__(self, text):
self.text = text
def _repr_html_(self):
return "<h1>" + self.text + "</h1>"
There are also two more powerful display methods:
_repr_mimebundle(include=None, exclude=None)
Should return a dictionary of multiple formats, keyed by mimetype, or a tuple of two dictionaries: data, metadata. If this returns something, other _repr_*_
methods are ignored. The method should take keyword arguments include
and exclude
, though it is not required to respect them.
Displays the object as a side effect; the return value is ignored. If this is defined, all other display methods are ignored.
The user can also register formatters for types without modifying the class:
from bar import Foo
def foo_html(obj):
return '<marquee>Foo object %s</marquee>' % obj.name
html_formatter = get_ipython().display_formatter.formatters['text/html']
html_formatter.for_type(Foo, foo_html)
# Or register a type without importing it - this does the same as above:
html_formatter.for_type_by_name('bar.Foo', foo_html)
Rarely, you might want to display a custom traceback when reporting an exception. To do this, define the custom traceback using _render_traceback_(self) method which returns a list of strings, one string for each line of the traceback. For example, the ipyparallel a parallel computing framework for IPython, does this to display errors from multiple engines.
Please be conservative in using this feature; by replacing the default traceback you may hide important information from the user.