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Deform Demo

Demonstration application for the Deform Python HTML form library.

This application is tested on Python versions 3.6, 3.7, 3.8, and 3.9, and PyPy3.

Online version


Docker version

Build the Docker image for deformdemo and tag it.

# docker build --tag pylons/deformdemo3:<version> .
docker build --tag pylons/deformdemo3:main .

Run the built image with Docker.

docker run -d -p 8000:8523 pylons/deformdemo3:main

Then in your browser, visit http://localhost:8000

To stop the docker container, find its NAME and issue the stop command.

docker ps -a
docker stop <value_from_NAMES_column>

From source

  • Create a virtual environment.

    python3 -m venv /path/to/my/env

    Hereafter /path/to/my/env will be referred to as $VENV in the following steps.

  • Clone deformdemo.

    git clone git://
  • cd to the newly checked out deformdemo package.

    cd deformdemo
  • Run pip install -e . using the virtual environment's python command.

    $VENV/bin/pip install -e .
  • While your working directory is still deformdemo, start the demo application.

    $VENV/bin/pserve demo.ini
  • Visit http://localhost:8523 in a browser to see the demo.

Install functional test requirements

The deformdemo application serves as a target for functional testing during Deform's development. A suite of Selenium tests may be run against a local instance of the demonstration application. It is wise to run these tests using the following steps before submitting a pull request.

First prepare the functional test environment by installing requirements. We will assume that you put your projects in your user directory, although you can put them anywhere.

cd ~/projects/deformdemo/

Install Python development and testing requirements

The following command will install requirements for development and testing of deformdemo. It performs editable installs of Colander and Deform into your virtual environment's src directory, and deformdemo's testing requirements into lib/<python.version>/site-packages directory.

$VENV/bin/pip install -Ur requirements-dev.txt

Install Firefox latest


Download the latest version of Firefox for your platform.

Open the .dmg (macOS), and drag the Firefox icon to:


Linux (Debian)

Use cURL or wget. See the Firefox download README.txt for instructions. For example on Linux:

cd ~/projects/deformdemo/
wget -O firefox-latest.tar.bz2 \

Decompress the downloaded file.

tar -xjf firefox-latest.tar.bz2


Install the latest release of geckodriver.

# macOS
tar -xzf geckodriver-v0.29.0-macos.tar.gz

# Linux (Debian)
tar -xzf geckodriver-v0.29.0-linux64.tar.gz


The functional tests require the installation of the GNU gettext utilities, specifically msgmerge and msgfmt. Use your package manager to install these requirements.


Use Homebrew.

brew install gettext
brew link gettext --force

If you ever have problems building packages, you can always unlink it.

brew unlink gettext

Linux (Debian)

apt-get install gettext
apt-get install gettext-base


Selenium was already installed via $VENV/bin/pip install -Ur requirements-dev.txt.

Running the Demo's Functional Tests

  • Start the deformdemo application as described above in "Running the Demo". Leave the terminal window running this application open, and open a second terminal window to perform the below steps.

  • In the second terminal window, go to the "deformdemo" checkout directory you created above in "Running the Demo".

    cd ~/projects/deformdemo
  • Set an environment variable to add your local checkout of Deform to your PATH. It must to be set before running tox or pytest, otherwise Firefox or Chrome will not start and will return an error message such as 'geckodriver' executable needs to be in PATH.

    export PATH=~/projects/deform:$PATH
  • Run the tests.


    $VENV is defined as it was in "Running the Demo" above.

  • You will (hopefully) see Firefox pop up and it will begin to display in quick succession the loading of pages. The tests will run for five or ten minutes.

  • Test success means that the console window on which you ran pytest shows a bunch of dots, a test summary, then OK. If it shows a traceback, FAILED, or anything other than a straight line of dots, it means there was an error.

  • Fix any errors by modifying your code or by modifying the tests to expect the changes you've made.

Testing an Alternate Renderer Implementation

  • Copy the demo.ini file from this demo package to your renderer's package.
  • Change the deform.renderer key in the demo.ini copy to point at your renderer (it's a Python dotted name).
  • Run pserve /path/to/your/copy/of/demo.ini.
  • Run the Selenium tests as above.