The code must be compatible with the oldest supported version of python as given on the Installation page.
In code, like the implementation of ASE, we must not use the
import * syntax. Import everything explicitly from exactly the
place where it’s defined:
from ase.io import read, write
Python Coding Conventions¶
Please run pep8 and pyflakes on your code before committing.
The rules for the Python part are almost identical to those used by the Docutils project:
Contributed code will not be refused merely because it does not strictly adhere to these conditions; as long as it’s internally consistent, clean, and correct, it probably will be accepted. But don’t be surprised if the “offending” code gets fiddled over time to conform to these conventions.
- 4 spaces per indentation level. No hard tabs.
- Very important: Read the Whitespace in Expressions and Statements section of PEP8.
- Avoid introducing trailing whitespaces.
- Try to use only 7-bit ASCII, no 8-bit strings.
- No one-liner compound statements (i.e., no
if x: return: use two lines & indentation), except for degenerate class or method definitions (i.e.,
class X: passis OK.).
- Lines should be no more than 78 characters long.
- Use “StudlyCaps” for class names.
- Use “lowercase” or “lowercase_with_underscores” for function, method, and variable names. For short names, maximum two words, joined lowercase may be used (e.g. “tagname”). For long names with three or more words, or where it’s hard to parse the split between two words, use lowercase_with_underscores (e.g., “note_explicit_target”, “explicit_target”). If in doubt, use underscores.
- Avoid lambda expressions, which are inherently difficult to understand. Named functions are preferable and superior: they’re faster (no run-time compilation), and well-chosen names serve to document and aid understanding.
- Avoid functional constructs (filter, map, etc.). Use list comprehensions instead.
- Use ‘single quotes’ for string literals, and “”“triple double
quotes”“” for docstrings. Double quotes are OK for
- Parentheses, ] and } must never be left alone, sad and lonesome on their own line.
Thus spake the Lord: Thou shalt indent with four spaces. No more, no less. Four shall be the number of spaces thou shalt indent, and the number of thy indenting shall be four. Eight shalt thou not indent, nor either indent thou two, excepting that thou then proceed to four. Tabs are right out.
- Get rid of as many
continuestatements as possible.
Writing documentation in the code¶
Here is an example of how to write good docstrings:
Run pep8 and pyflakes on your code¶
$ pep8 --ignore W293,E129 filename.py $ pyflakes filename.py
$ alias check="python -m ase.utils.stylecheck" $ check filename.py
pyflakes like this:
pip install pep8 pyflakes.
Run autopep8.py on your code¶
Another method of enforcing PEP8 is using a tool such as autopep8.py. These tools tend to be very effective at cleaning up code, but should be used carefully and code should be retested after cleaning it. Try:
$ autopep8.py --help
There is a common issue with pep8 where spaces are added around the power operator. Code such as “x**2” should not be changed to “x ** 2”. This issue is not fixed in pep8 as of the time of this writing, but a small change to autopep8 has been effective to prevent this change.