Software Development

Dr Andy Evans

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Development Processes

Considerable debate exists around how best to manage software development.
Most proposed 'processes' have a parentage in the 'Waterfall Model'; roughly:

Requirements
Design
Coding
Testing
Installation
Maintenance

Like a good many parents who try their best, its children have nothing good to say about it.

Critiques

Largely focused on the fact that software was never fully completed, but always being re-visited at different scales. In particular, it is unhelpful not to go back to users and consult once a basic system is drafted.
Popular alterative is Iterative and Incremental development, where, after initial Requirements are outlined, there is a cycling through the development units, taking important and high-risk elements first.
This is sometimes combined with the Waterfall model as the 'Iterfall model'. Experience suggests the broad sweep of this matches with beginner's natural inclinations.

New processes

Based on the Iterative and avoiding the over-management of the Waterfall method: Agile software development processes include:
- Rational Unified Process
- Extreme Programming
- Kanban and SCRUM for communication
- Short development sprints
- Continuous Integration
Main issue is to concentrate on user needs.

Kanban and SCRUM are widely used for communication between large development teams. Taken from process design research: Kanban Toyota - Japanese for ticket, have swim lanes on a board and the aim is to move tickets from a backlog across a board as quickly as possible in an accepted area. Every 2 weeks or so a 'Product Owner' will either accept or reject development progress against a ticket. SCRUM is a way of making sure the whole development team knows what is going on, normally a ten minute stand up meeting around a Kanban board highlighting progress, issues and blockers so that everyone in the team is aware if they are needed to progress a particular ticket. Key to most of these development techniques is a short development sprint which puts the user in the driving seat and ensures critical must-have development is completed first. It also provides continuous feedback for the development team. Continuous integration ensures that all developers integrate their code, rather than having two developers working in isolation producing modules that will not work together.

UML

An intrinsic part of the development process.
From: Use Cases
Through: Class Diagrams
To: Activity Diagrams

Initial consultation

User consultation is a vital part of development.
Users should be consulted first. If the users don't like your software, you're sunk.
Find out what people expect to get from the system before adding extras. If it helps draw UML User Case diagrams.
User Cases can be used to break a large project up into smaller bits. Do the most difficult important bits first if possible!
However, watch for "feature creep".

Usability testing

When you think you have a bit users are interested in up and running, test its 'usability'.
Sit your users down with the software and get them to play with it.
It's useful to set them common tasks to do.
See how long they take to do stuff, and what they do that's unexpected. Some companies use mirrored windows.
Remember, users don't make mistakes - it's your fault if you lead them the wrong way!

Development stages

Refining user requirements.
Dividing code (e.g. by important high-risk functions first).
Keeping users informed.
Development.
Usability testing.
Bug hunting.
Refactoring.
Alpha and Beta testing.
Releases.
Deciding on the next set of functions to tackle.
Increasingly releases tackle a few functions on a short timescale rather than major releases with a longer gap ("Release Early and Release Often": "RERO").

Summary

Always design assuming the user...
- Will experiment rather than read the manual.
- Will base these experiments on what they expect to find.
Always base the software design around what the user wants.
Always test the user's opinions and the usability as you develop.

Licensing

Different options on a spectrum:
Open source.
Maintenance contracts.
Open standards.
Community built.
Freeware.
Adware.
Commercial.

Installing

Broadly speaking, you have five levels of distribution:
1. Send them the Python files to run / package as a zip.
2. Add a .bat or .sh file to run the files.
3. Produce a proper distribution with a setup.py file to install at the command line.
4. Upload to PyPi and configure for online installation through pip.
5. Build a binary for a specific operating system.

Distributing and installing

The starting point for either of the two more complicated options is:
https://packaging.python.org/
Chances are, this is all you'll need.
For more complicated projects, there's:
https://setuptools.readthedocs.io/en/latest/
Which works with:
https://docs.python.org/3/library/distribution.html
See also:
https://docs.python.org/3/distributing/index.html

Executables

If you actually want to produce compiled versions for a specific operating system, see:
https://docs.python.org/3/tutorial/appendix.html#executable-python-scripts
https://docs.python.org/3/faq/programming.html#how-can-i-create-a-stand-alone-binary-from-a-python-script

Internationalisation

You may also want to consider internationalising your code (for example, responding to different locations with different interface text). The starting point for this is:
https://docs.python.org/3/library/gettext.html#internationalizing-your-programs-and-modules
https://docs.python.org/3/library/locale.html

Summary

Getting a strong project outline at the start will help you resource a project, as will having a clear delimitation of coding activities.
However, project frameworks need to have flexibility built in to cope with project evolution. Start with an ordered list of functionalities, but consult with users frequently.
Look into formal software development processes if you have to work with teams.