SymPy Gamma is a simple web application based on Google App Engine that executes and displays the results of SymPy expressions as well as additional related computations, in a fashion similar to that of Wolfram|Alpha. For instance, entering an integer will display prime factors, digits in the base-10 expansion, and a factorization diagram. Entering a function will give its docstring; in general, entering an arbitrary expression will provide the derivative, integral, series expansion, plot, and roots.

Google App Engine has intrinsic 30 second request handling limit, so each evaluation request is a subject to this limit. There are also other limits related to memory consumption, output size, etc. (see Google App Engine documentation for details). Each result is evaluated in a separate request, so (for instance) an integral that takes too long will not prevent the other information from loading.

Download and unpack most recent Google App Engine SDK for Python from http://code.google.com/appengine/downloads.html, e.g.:

$ wget http://googleappengine.googlecode.com/files/google_appengine_1.5.1.zip
$ unzip google_appengine_1.5.1.zip

On the Mac, it is a disk image with an application, which you should drag to your Applications folder. Open the program and install the symlinks (it should ask you the first time you open the application, but if it doesn't, choose "Make Symlinks..." from the GoogleAppEngineLauncher menu). Note that you will have to do this again each time you update the AppEngine program.

Then clone sympy_gamma repository:

$ git clone git://github.com/sympy/sympy_gamma.git
$ cd sympy_gamma

We use submodules to include external libraries in sympy_gamma:

$ git submodule init
$ git submodule update

This is sufficient to clone appropriate repositories in correct versions into sympy_gamma (see git documentation on submodules for information).

Now you are ready to run development web server:

$ ../google_appengine/dev_appserver.py .

On the Mac, just run:

$ dev_appserver.py .

(make sure you installed the symlinks as described above).

I couldn't figure out how to make it work in the GUI (it won't find the sympy git submodule). If you figure out how to do it, please update this file and send a patch describing how to do it.

This is a local server that runs on port 8080 (use --port option to change this). Open a web browser and go to http://localhost:8080. You should see GUI of SymPy Gamma.

Before updating the the sympy_gamma app (the official one), you need to do two things. First you need to bump the version in the app.yaml file. Just change the second line ("version") to one more, and commit it (git commit app.yaml -m "Bump version to NN", where NN is the new version) and push it. Second, you need to go to the Versions section of the sympy_gamma dashboard at appspot.com and delete the oldest version, as we can only upload ten versions at a time.

Assuming that sympy_gamma works properly (also across different mainstream web browsers), you can upload your changes to Google App Engine:

$ ../appcfg.py update .

Or, in Mac OS X, just open the GoogleAppEngineLauncher program, add the project if you haven't already, and click "Deploy" in the toolbar. And then it should just work (follow the log that comes up to see.

This requires admin privileges to http://sympy-gamma-hrd.appspot.com. If you don't have access to this App Engine application, but want to test it, see the instructions in the Testing on the App Engine section below.

Finally, go to http://NN.sympy-gamma-hrd.appspot.com, where NN is the version you just uploaded, and make sure that it works. If it does, go to the Versions section of the sympy_gamma dashboard, and set this as the new default version. If there are any issues, you can roll back to the previous version from this same screen.

It's usually a good idea to test big changes on the App Engine itself before deploying, as dev_appserver.py can only simulate the App Engine. Currently, there is no testing server set up as there is for SymPy Live. However, you can set up your own testing server (it's free, though it requires a cell phone to set up).

Either way, to test, you will need to edit the app.yaml file. You should edit the first line, application, to the name of the testing application (like sympy-gamma-tests), and the second line to the version number you want to use.

You should not actually commit these changes to app.yaml, as the official version should still use the sympy-gamma-hrd application. Therefore, it is recommended that you run:

git update-index --assume-unchanged app.yaml

This will make git ignore all changes to the app.yaml file, so that commands like git commit -a will not commit them. This command works on the local level only, so you don't need to worry about it affecting other people who pull your branch.

If you later want to commit an actual change to app.yaml (e.g., to modify some metadata, or to bump the version as described above), you need to run:

git update-index --no-assume-unchanged app.yaml

This will undo the above command, so that git will recognize changes to the file again.

If you have a test app online, remember to update it every time you update a pull request, so that others can easily review your work, without even having to use dev_appserver.py.

Make sure SymPy Gamma works in major mainstream web browsers. This includes Chrome, Firefox, Safari and Internet Explorer. Be extra cautious about trailing commas in JavaScript object and arrays. IE doesn't allow them, so you have to remove them, if any were introduced. Also test on mobile browsers, such as Safari for iOS and Chrome for Android, on both smartphones and tablets; Gamma has layouts for phones, tablets, and desktop browsers. The viewport emulation built into the developer tools of desktop browsers can help with this testing, but there may be differences that need to be checked with an actual device. (In Google Chrome, for instance, open up the developer console, click the gear icon in the lower right, then select Overrides.)

GAE development server allows to use any Python interpreter, but Google App Engine uses Python 2.5, so if the default Python isn't 2.5, then make sure to test your changes to the server part, if it runs properly on 2.5. Also don't use any modules that aren't supported by GAE. Note that GAE now supports Python 2.7 and that this is what is currently deployed.

In projects that don't use submodules, pulling changes boils down to:

$ git pull origin master

in the simplest case. SymPy Gamma, however, requires additional effort:

$ git submodule update

The above command assures that if there were any changes to submodules of the super-project, then those submodules will get updated to new versions. This is related to the following section.

Make sure that you followed instructions above and SymPy's submodule is properly initialized. Assuming that you are in the directory where SymPy Gamma was cloned, issue:

$ cd sympy/
$ git fetch origin
$ git checkout sympy-0.7.0
$ cd ..
$ git add .
$ git commit -m "Updated SymPy to version 0.7.0"

Now if you issue:

$ git show -v

you should get:

commit 5138e824dc9fd46c243eea2d7c9581a9e58feb08
Author: Mateusz Paprocki <mattpap@gmail.com>
Date:   Wed Jul 6 07:45:19 2011 +0200

    Updated SymPy to version 0.7.0

    diff --git a/sympy b/sympy
    index df7a135..c9470ac 160000
    --- a/sympy
    +++ b/sympy
    @@ -1 +1 @@
    -Subproject commit df7a135a4ff7eca361ebbb07ccbeabf8654a8d80
    +Subproject commit c9470ac4f44e7dacfb026cf74529db3ec0822145

This was done for SymPy's version 0.7.0, so in future updates of SymPy replace 0.7.0 with appropriate newer version (e.g. 0.7.1) and you are done (of course particular SHA signatures will be different in your case). If unsure, refer to git help submodule or git book: http://book.git-scm.com/5_submodules.html.

Originally realized by Ondřej Čertík (a core SymPy developer) as an online Python notebook and Wolfram|Alpha clone for the Google App Engine that would showcase SymPy. The notebook was eventually removed in favor of using SymPy Live.