In this slides, the author demonstrates many software development practices in Python. Including: runtime environment setup, source code management, version control, unit test, coding convention, code duplication, documentation and automation.

1. Software Development Practices
in Python
Jimmy Lai
r97922028 [at] ntu.edu.tw
http://tw.linkedin.com/pub/jimmy-lai/27/4a/536
2013/02/14

2. Outline
1. Runtime Environment: virtualenv and pip
2. Source Code Management:
– Version control: Mercurial
– Unit test: code coverage
• doctest
• nosetests
– Coding convention: PEP8
– Code duplication: clonedigger
3. Documentation: Sphinx
4. Automation: fabric
Software Development Practice in Python 2

3. Demo Code
$ hg clone https://bitbucket.org/noahsark/slideshare
Demo Codes are in python_demo dir.
Files:
1. my_operator.py, my_operator_test.py
2. fabfile.py
Software Development Practice in Python 3

4. Runtime Environment - virtualenv
• Isolates runtime environment dependency of
your python project.
$ virtualenv --no-site-packages env_name
$ . env_name/bin/activate
# enter the virtual environment
$ pip install package_name
# install python packages
Software Development Practice in Python 4

5. Source Code Management
Version Control - Mercurial
• Distributed repositories Ignore some files shown in
• Common commands: `hg status`
$ hg clone File: .hgignore
ssh://hg@bitbucket.org/noahs
syntax: glob
ark/slideshare
$ hg commit *.pyc
*.swp
$ hg push docs/build
$ hg fetch
• Useful hooks:
http://pypi.python.org/pypi/hghooks/
Software Development Practice in Python 5

6. Source Code Management
Unit Test - nose
• nose def setup():
global test_case_1
– Simpler and easier than test_case_1 = (1, 2)
unittest
def teardown():
– Nose tests in XXX_test.py pass
and functions named
test_XXX def adder(a, b):
return a + b
$ pip install nose
@with_setup(setup, teardown)
# install def test_adder():
$ nosetests expected = 3
actual = adder(test_case_1[0],
# nose tests and execute test_case_1[1])
nt.assert_equal(actual, expected)
Software Development Practice in Python 6

7. Source Code Management
Unit Test - doctest
• Doctest def adder(a, b):
'''
– Write test in the >>> adder(2, 3)
docstring of function 5
– Easy and simple '''
return a + b
– The test case is a usage
example and appears in
documents.
• http://docs.python.org/
2/library/doctest.html
Software Development Practice in Python 7

8. Source Code Management
Unit Test – Test Coverage
• Test is the shield of Name Stmts Miss Cover Missing
-------------------------------------------------------
code. Test coverage is python_demo 0 0 100%
the percentage of code python_demo.fabfile 23 15 35% 13-14
be covered by test cases. python_demo.my_operator 6 0 100%
-------------------------------------------------------
• Coverage rate over 80% TOTAL 29 15 48%
is good.
$ pip install coverage
$ nosetests --with-coverage
# run coverage by nose
Software Development Practice in Python 8

9. Source Code Management
Coding Convention – PEP8
• http://www.python.org/dev/peps/pep-0008/
• Code layout consistency:
– Usage of indentation, space, blank line
– Naming convention
– Programming recommendations
• Setup PEP8 checking as mercurial hook to
ensure the consistency.
pretxncommit.pep8 = python:hghooks.code.pep8hook
Software Development Practice in Python 9

10. Source Code Management
Code Duplication - clonedigger
• Duplicated codes should be refactored as
reusable module
$ pip install clonedigger
$ clonedigger . Output example
$ firefox output.html
Software Development Practice in Python 10

11. Documentation - Sphinx
• Document is important for reuse
• Document type:
– Tutorial, system architecture
– Functions, modules explanation
• Sphinx: write docs in reStructuredText
$ pip install sphinx
Refer to http://www.slideshare.net/jimmy_lai/documentation-with-sphinx
for more detail.
Software Development Practice in Python 11

12. Automation - fabric
• Automation reduces • Common tasks suitable
repeating efforts. for automation:
• Things you do for the – Build executable
second time is worth to – Build document (fab doc)
automate. – Run unit tests (fab test)
$ pip install fabric – Setup Runtime
Environment (fab setup)
– Deploy
• See fabfile.py for more
examples.
Software Development Practice in Python 12