Important

This documentation covers IPython versions 6.0 and higher. Beginning with version 6.0, IPython stopped supporting compatibility with Python versions lower than 3.3 including all versions of Python 2.7.

If you are looking for an IPython version compatible with Python 2.7, please use the IPython 5.x LTS release and refer to its documentation (LTS is the long term support release).

Module: lib.pretty

Python advanced pretty printer. This pretty printer is intended to replace the old pprint python module which does not allow developers to provide their own pretty print callbacks.

This module is based on ruby’s prettyprint.rb library by Tanaka Akira.

Example Usage

To directly print the representation of an object use pprint:

from pretty import pprint
pprint(complex_object)

To get a string of the output use pretty:

from pretty import pretty
string = pretty(complex_object)

Extending

The pretty library allows developers to add pretty printing rules for their own objects. This process is straightforward. All you have to do is to add a _repr_pretty_ method to your object and call the methods on the pretty printer passed:

class MyObject(object):

    def _repr_pretty_(self, p, cycle):
        ...

Here’s an example for a class with a simple constructor:

class MySimpleObject:

    def __init__(self, a, b, *, c=None):
        self.a = a
        self.b = b
        self.c = c

    def _repr_pretty_(self, p, cycle):
        ctor = CallExpression.factory(self.__class__.__name__)
        if self.c is None:
            p.pretty(ctor(a, b))
        else:
            p.pretty(ctor(a, b, c=c))

Here is an example implementation of a _repr_pretty_ method for a list subclass:

class MyList(list):

    def _repr_pretty_(self, p, cycle):
        if cycle:
            p.text('MyList(...)')
        else:
            with p.group(8, 'MyList([', '])'):
                for idx, item in enumerate(self):
                    if idx:
                        p.text(',')
                        p.breakable()
                    p.pretty(item)

The cycle parameter is True if pretty detected a cycle. You have to react to that or the result is an infinite loop. p.text() just adds non breaking text to the output, p.breakable() either adds a whitespace or breaks here. If you pass it an argument it’s used instead of the default space. p.pretty prettyprints another object using the pretty print method.

The first parameter to the group function specifies the extra indentation of the next line. In this example the next item will either be on the same line (if the items are short enough) or aligned with the right edge of the opening bracket of MyList.

If you just want to indent something you can use the group function without open / close parameters. You can also use this code:

with p.indent(2):
    ...

Inheritance diagram:

Inheritance diagram of IPython.lib.pretty
copyright:

2007 by Armin Ronacher. Portions (c) 2009 by Robert Kern.

license:

BSD License.

10 Classes

class IPython.lib.pretty.PrettyPrinter(output, max_width=79, newline='\n', max_seq_length=1000)

Bases: _PrettyPrinterBase

Baseclass for the RepresentationPrinter prettyprinter that is used to generate pretty reprs of objects. Contrary to the RepresentationPrinter this printer knows nothing about the default pprinters or the _repr_pretty_ callback method.

__init__(output, max_width=79, newline='\n', max_seq_length=1000)
begin_group(indent=0, open='')

Begin a group. The first parameter specifies the indentation for the next line (usually the width of the opening text), the second the opening text. All parameters are optional.

break_()

Explicitly insert a newline into the output, maintaining correct indentation.

breakable(sep=' ')

Add a breakable separator to the output. This does not mean that it will automatically break here. If no breaking on this position takes place the sep is inserted which default to one space.

end_group(dedent=0, close='')

End a group. See begin_group for more details.

flush()

Flush data that is left in the buffer.

text(obj)

Add literal text to the output.

class IPython.lib.pretty.RepresentationPrinter(output, verbose=False, max_width=79, newline='\n', singleton_pprinters=None, type_pprinters=None, deferred_pprinters=None, max_seq_length=1000)

Bases: PrettyPrinter

Special pretty printer that has a pretty method that calls the pretty printer for a python object.

This class stores processing data on self so you must never use this class in a threaded environment. Always lock it or reinstanciate it.

Instances also have a verbose flag callbacks can access to control their output. For example the default instance repr prints all attributes and methods that are not prefixed by an underscore if the printer is in verbose mode.

__init__(output, verbose=False, max_width=79, newline='\n', singleton_pprinters=None, type_pprinters=None, deferred_pprinters=None, max_seq_length=1000)
pretty(obj)

Pretty print the given object.

class IPython.lib.pretty.Printable

Bases: object

class IPython.lib.pretty.Text

Bases: Printable

__init__()
class IPython.lib.pretty.Breakable(seq, width, pretty)

Bases: Printable

__init__(seq, width, pretty)
class IPython.lib.pretty.Group(depth)

Bases: Printable

__init__(depth)
class IPython.lib.pretty.GroupQueue(*groups)

Bases: object

__init__(*groups)
class IPython.lib.pretty.RawText(value)

Bases: object

Object such that p.pretty(RawText(value)) is the same as p.text(value).

An example usage of this would be to show a list as binary numbers, using p.pretty([RawText(bin(i)) for i in integers]).

__init__(value)
class IPython.lib.pretty.CallExpression(_CallExpression__name, *args, **kwargs)

Bases: object

Object which emits a line-wrapped call expression in the form __name(*args, **kwargs)

__init__(_CallExpression__name, *args, **kwargs)
class IPython.lib.pretty.RawStringLiteral(value)

Bases: object

Wrapper that shows a string with a r prefix

__init__(value)

4 Functions

IPython.lib.pretty.pretty(obj, verbose=False, max_width=79, newline='\n', max_seq_length=1000)

Pretty print the object’s representation.

IPython.lib.pretty.pprint(obj, verbose=False, max_width=79, newline='\n', max_seq_length=1000)

Like pretty but print to stdout.

IPython.lib.pretty.for_type(typ, func)

Add a pretty printer for a given type.

IPython.lib.pretty.for_type_by_name(type_module, type_name, func)

Add a pretty printer for a type specified by the module and name of a type rather than the type object itself.