.. _chapter-faq-contribute:
=========================
FAQ: Contributing to Sage
=========================
How can I get started contributing to Sage?
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This is a quick guide for anyone who wants to contribute to Sage. It
is intended especially for anyone who is new to computer
programming. First, Sage's main programming language is
`Python `_.
Some parts of Sage can be written in other languages, especially the
components that do the heavy number crunching, but most native
functionality is done using Python, including "glue code". One of the
good aspects of Python that Sage inherits is that working code is
considered more valuable than just fast code. Fast code is valuable,
but clean, readable code is important. In the mathematics community,
inaccurate results are unacceptable. Correctness comes before
optimization. In the following paper
* D. Knuth. Structured Programming with go to Statements.
*ACM Journal Computing Surveys*, 6(4), 1974.
Don Knuth observes that: "We should forget about small efficiencies,
say about 97% of the time: premature optimization is the root of all
evil."
If you do not know Python, you should start learning that language. A
good place to start is the
`Python Official Tutorial `_
and other documents in the
`Python standard documentation `_.
Another good place to take a look at is
`Dive Into Python `_
by Mark Pilgrim, which may be pretty helpful on some specific topics
like test-driven development. The book
`Building Skills in Python `_
by Steven F. Lott is suitable for anyone who is already comfortable
with programming.
In the meantime, you can grab your copy of the Sage
source and familiarize yourself with the
`git `_ version control system. Once you are comfortable with Python itself, which is
pretty fast for basics, you can start using Sage. If you want, you can
try to learn Python by using Sage, but that is not recommended because
it is helpful to know what is pure Python and when Sage is doing its
"magic". There are many things that work in Python but not in Sage,
and vice versa.
Then take a look at the
`official development guide `_
for Sage. At a minimum, the first chapter in that guide is required
reading for any Sage developer. Also pay special attention to the
`trac guidelines `_.
You can also join the
`sage-devel `_
mailing list and hang around on the
``#sage-devel`` IRC channel on
`freenode `_.
The best way to become familiar with the Sage development process is
to choose a ticket from the
`trac server `_
and review the proposed changes contained in that ticket. If you want
to implement something, it is a good practice to discuss your ideas on
the ``sage-devel`` mailing list first, so that other developers have a
chance to comment on your ideas/proposals. They are pretty open to new
ideas, too, like all mathematicians should be.
I'm not a programmer. Is there another way I can help out?
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Yes. Like any free open source software project, there are numerous
ways in which you could help out within the Sage community. And
programming is one of many ways to contribute. If you can speak, read,
and write in another (natural) language, there are many ways in which
your contribution would be very valuable to the whole Sage
community. Say you know Italian. Then you can write a Sage tutorial in
Italian, or help out with translating the official Sage tutorial to
Italian. For the graphics designers or artistically creative, you can
help out with improving the design of the Sage website. Or you can
cast your critical artistic eyes over the Sage notebook interface and
find out where it needs improvement.
Many people like writing technical tutorials. One of the joys of doing
so is that you also learn something new in the process. At the same
time, you communicate your knowledge to beginners, a skill which is
useful in fields other than technical writing itself. A main point
about technical writing is that you communicate a technical subject to
beginners, so keep technical jargons to a minimum. Darrell Anderson
has written some
`tips on technical writing `_,
which you are highly recommended to read. The above is a very short
list. There are many, many more ways in which you can help out. Feel
free to send an email to the
`sage-devel `_
mailing list to ask about possible ways in which you could help out,
or to suggest a project idea.
Where can I find resources on Python or Cython?
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Here is an incomplete list of resources on Python and Cython. Further
resources can be found by a web search.
**General resources**
* `Cython `_
* `pep8 `_
* `py2depgraph `_
* `pycallgraph `_
* `PyChecker `_
* `PyFlakes `_
* `Pylint `_
* `Python `_ home page and the
`Python standard documentation `_
* `Snakefood `_
* `Sphinx `_
* `XDot `_
**Tutorials and books**
* `Building Skills in Python `_
by Steven F. Lott
* `Cython Tutorial `_
by Stefan Behnel, Robert W. Bradshaw, and Dag Sverre Seljebotn
* `Dive into Python `_ by Mark Pilgrim
* `Dive Into Python 3 `_ by Mark Pilgrim
* `Fast Numerical Computations with Cython `_
by Dag Sverre Seljebotn
* `How to Think Like a Computer Scientist `_
by Jeffrey Elkner, Allen B. Downey, and Chris Meyers
* `Official Python Tutorial `_
**Articles and HOWTOs**
* `decorator `_
* `Functional Programming HOWTO `_
by A. M. Kuchling
* `Python Functional Programming for Mathematicians `_
by Minh Van Nguyen
* `Regular Expression HOWTO `_
by A. M. Kuchling
* `reStructuredText `_
* `Static Code Analizers for Python `_
by Doug Hellmann
Are there any coding conventions I need to follow?
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You should follow the standard Python conventions as documented at
`PEP 0008 `_
and
`PEP 0257 `_.
Also consult the Sage Developer's Guide, especially the chapter
`Conventions for Coding in Sage `_.
I submitted a bug fix to the trac server several weeks ago. Why are you ignoring my patch?
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We are not trying to ignore your patch. People who work on Sage do so
in their free time. With hundreds of open tickets of varying degrees of
impacts on the whole Sage community, people who work on tickets need
to prioritize their time and work on those tickets that interest
them. Sometimes you may be the only person who understands your
patch. In that case, you are encouraged to take extra care to make it
as easy as possible for anyone to review your patch. Here are some
tips on making your patch easy to review:
* Have you clearly described the problem your patch is trying to
solve?
* Have you provided any background information relevant to the problem
your patch is trying to solve? Such information include links to
online resources and any relevant papers, books and reference
materials.
* Have you clearly described how your patch solves the problem under
consideration?
* Have you clearly described how to test the changes in your patch?
* Have you listed any tickets that your patch depends on?
* If there are more than one patch, have you clearly stated the order
in which those patches are to be applied?
* Does your patch
`follow relevant conventions `_
as documented in the Developer's Guide?
If your patch stands no chance of being merged in the Sage source
tree, we will not ignore your patch but simply close the relevant
ticket with an explanation why we cannot include your changes.
When and how might I remind the Sage community of a patch I care about?
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You are encouraged to take extra care in how you remind the Sage
community of a patch you want to get merged into the Sage source
tree. There might be an upcoming bug squash sprint or an upcoming Sage
Days workshop that relates to your patch. Monitor the relevant Sage
mailing lists and respond politely to any relevant email threads, with
clear explanation on why your patch is relevant. Monitor the
``#sage-devel`` IRC channel, taking care to strategically time your
reminders.
I wrote some Sage code and I want it to be integrated into Sage. However, after renaming my file ``a.sage`` to ``a.py``, I got syntax errors. Do I have to rewrite all my code in Python instead of Sage?
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The basic answer is yes, but rewriting is a big word for what is
really needed. There is little work to do since Sage mostly follows
Python syntax. The two main differences are handling of integer (see
also the `afterword`_ for more on the sage preparser), and the
necessity to import what you need.
- **Handling of integer:** You need to take care of the following
changes:
- Notation for exponentiation: In Python ``**`` means exponentiation
and ``^`` means "xor".
- If you need to return an integer to the user, write ``return
Integer(1)`` instead of ``return 1``. In Python, 1 is a python
``int``, and ``Integer(1)`` is a Sage/Gmp integer. In addition,
``Integer`` are much more powerful than ``int``; for
example, they know about being prime and factorization.
- You should also notice that ``2 / 3`` no longer means
``Integer(2) / Integer(3)`` and returns ``2/3``, but rather
``int(2) / int(3)``, and therefore returns ``0`` due to integer
division where it deregards any remainder. If you are dealing with
``Integer`` but you really need an integer division you can use
``Integer(2) // Integer(3)``.
- **Importing stuff:** The second big change is the necessity to
import everything what you need. More precisely, each time you use
some Sage function, you need to import it at the beginning of the
file. For example, if you want ``PolynomialRing``, you need to
write::
from sage.rings.polynomial.polynomial_ring_constructor import PolynomialRing
You can ask Sage where to find ``PolynomialRing`` using::
sage: PolynomialRing.__module__
'sage.rings.polynomial.polynomial_ring_constructor'
This also corresponds to the path starting after ``site-packages``
given when you ask Sage for ``PolynomialRing`` help. For example,
if you call ``PolynomialRing?``, you get::
Type: function
[...]
File: /home/florent/src/Sage/sage/local/lib/python2.6/site-packages/sage/rings/polynomial/polynomial_ring_constructor.py
[...]
.. _afterword: http://www.sagemath.org/doc/tutorial/afterword.html