# Third-party Libraries in Python 2.7 - Google App Engine - Google Code

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# Third-party Libraries in Python 2.7

In addition to the Python standard library, the App Engine APIs and tools, the App Engine Python runtime environment includes several third-party libraries that your application can use. Some of these libraries have been customized or reimplemented to run within the App Engine sandbox restrictions. This page documents which libraries are available and how the App Engine implementations differ from the original versions.

- Django
- lxml
- jinja2
- MarkupSafe
- NumPy
- PIL
- PyCrypto
- setuptools
- WebOb
- YAML

Third-party libraries must be specified in `app.yaml`, and this configuration is different than in Python 2.5 (see Configuring Libraries for details). The following sample library element from `app.yaml` shows how to specify all of the available libraries with the most current version:

    libraries:
    - name: Django
      version: "1.2"
    - name: jinja2
      version: "2.6"
    - name: lxml
      version: "2.3"
    - name: MarkupSafe
      version: "0.15"
    - name: NumPy
      version: "1.6.1"
    - name: PIL
      version: "1.1.7"
    - name: PyCrypto
      version: "2.3"
    - name: SetupTools
      version: "0.6c11"
    - name: WebApp2
      version: "2.3"
    - name: WebOb
      version: "1.1.1"
    - name: yaml
      version: "3.10"

## Django

Django is a full-featured web application framework for Python. It provides a full stack of interchangable components, including dispatch, views, middleware, and templating components, and many others.

The Django data modeling interface is not compatible with the App Engine datastore. You can use the App Engine data modeling libraries in your Django applications. However, third-party Django applications that use the Django data modeling interface—most notably Django's Admin application—may not work with App Engine directly.

Warning! The App Engine Python 2.7 environment supports version 1.2 only. If you are upgrading to Python 2.7 and currently use Django version 0.96 or 1.0, you must upgrade your application and use version 1.2. See Porting Your Apps from Django .96 to 1.0 for upgrade details.

To use Django in Python 2.7, specify the WSGI application and Django library in `app.yaml`:

    ...
    handlers:
    - url: /.*
      script: main.app  # a WSGI application in the main module's global scope

    libraries:
    - name: django
      version: "1.2"

The `use_library()` function provided by the `google.appengine.dist` package is unavailable in Python 2.7.

Django 1.2 requires that the `DJANGO_SETTINGS_MODULE` environment variable be set to the name of your Django settings module, typically `'settings'`, before packages are imported. If your Django settings module is something other than `settings.py`, adjust your `main.py` file accordingly:

    import os
    # specify the name of your settings module
    os.environ['DJANGO_SETTINGS_MODULE'] = 'myapp.settings'

    import django.core.handlers.wsgi
    app = django.core.handlers.wsgi.WSGIHandler()

## lxml

The lxml toolkit provides easy-to-use functions for processing XML and HTML using Python. Python 2.7 provides lxml version 2.3.

## jinja2

jinja2 is a template engine for Python. WebApp templates are deprecated in Python 2.7, and jinja2 provides an alternative. The Python 2.7 environment supports jinja2 version 2.6.

## MarkupSafe

MarkupSafe provides a safe string for XML, HTML, and XHTML markup in Python. Python 2.7 supports version 0.15.

Note: enabling this library will make jinja2 template rendering faster.

## NumPy

NumPy provides a number of useful data processing tools. Python 2.7 provides version 1.6.1 of this library.

## PIL

The Python Imaging Library (PIL) provides image processing functions. Python 2.7 provides version 1.1.7 of this library.

## PyCrypto

The Python Cryptography Toolkit, also known as PyCrypto, provides cryptography functions such as random number generation. Python 2.7 provides PyCrypto 2.3.

## SetupTools

setuptools makes it easier to download, build, install, upgrade, and uninstall Python packages. Python 2.7 supports version 0.6c11.

## WebOb

WebOb is an object-oriented interface for HTTP requests and responses. App Engine uses WebOb as part of the webapp web application framework. The environment provides WebOb 1.1.1.

## YAML

YAML is a data format for human-readable message serialization. The App Engine Python SDK uses YAML as the format for its configuration files. The environment provides the YAML parsing libraries for Python, PyYAML 3.10.