1. nishio
  2. prettierprint



A prettier print


Python's standard pretty print library (pprint) doesn't support user defined class. Once I wanted to print Python's AST prettier, however it's not possible to use "pprint" for the purpose.

What is it?

This library is an implementation in Python of "A prettier print" introduced by Philip Wadler.


The algorithm was also implemented in Ruby's standard library: prettyprint.rb.



The purpose of this library is to give prettyprint ability on your class. In examples/show_ast.py you can see such examples. Here are small samples.

>>> from prettier import *
>>> docs = [Text("1. abc"), Text("2. abc"), Text("3. abc")]

# fill given space
>>> print(pretty(40, fill(docs)))
1. abc 2. abc 3. abc

>>> print(pretty(13, fill(docs)))
1. abc 2. abc
3. abc

>>> print(pretty(8, fill(docs)))
1. abc
2. abc
3. abc

# horizontal only
>>> print(pretty(1, spread(docs)))
1. abc 2. abc 3. abc

# vertical only
>>> print(pretty(100, stack(docs)))
1. abc
2. abc
3. abc

# when there isn't enough space to put horizontal, put vertical
>>> print(pretty(20, stack_or_spread(docs)))
1. abc 2. abc 3. abc

>>> print(pretty(13, stack_or_spread(docs)))
1. abc
2. abc
3. abc

# when there isn't enough space to put horizontal, use indent
>>> print(pretty(10, can_break_with_nest(docs)))
1. abc
  2. abc
  3. abc


$ easy_install prettier


Read the doctest please.


0.93 (2010-09- not released yet)

  • High-level API spread 's result should be flatten
  • add PrettiePrinter class in order to change indent width, newline character and default width
  • reuse Text(" "). There were some literal " ". It seems bad. Line() was already reused.

0.92 (2010-09-02)

  • Relative file("README.rst") fail on PyPI server. Fixed the bug in setup.py. (thanks Odagiri)
  • Because I didn't write MANIFEST.in, README.rst wasn't included in source distribution. Add it. (thanks matsubara)
  • PEP8 discouraged underscores in module name. Renamed it. (thanks Odagiri)

0.91 (2010-09-02)

  • Because I did $ python setup.py sdist bdist bdist_egg upload, there comes "dumb" binary. Removed bdist.

0.9 (2010-09-02)

  • first release


  • Make a function pprint(obj) which work like standard pprint.pprint

When the goal is achived the version goes 1.0.

For developer(include me)

Here is the repository: https://bitbucket.org/nishio/prettierprint

Don't forget to run test and confirm tests cover all code:

$ coverage run prettier/__init__.py && coverage html

Don't forget to test README.rst is valid (thanks SHIMIZUKAWA):

$ rst2html.py README.rst > README.html

When you relaese new version, don't put bdist option. (thanks SHIMIZUKAWA):

$ python setup.py sdist bdist_egg upload


Same as Python 3.0.


  • Takayuki SHIMIZUKAWA <shimizukawa at gmail com>
  • Atsushi Odagiri <aodagx at gmail com>
  • yutaka matsubara <yutaka matsubara at gmail com>


NISHIO Hirokazu <nishio (dot) hirokazu (at) gmail (dot) com>