Your contribution should fulfill the criteria provided below.

Styleguide for the codebase#

  • Functions have no side effect. : If you modify a mutable argument, make a copy at the beginning of the function.

  • Deep modules. : This is a term coined by John Ousterhout. A deep module is a module that has just one public function. This function calls the private functions (i.e. functions that start with an underscore) defined further down in the module and reads almost like a table of contents to the whole module.

  • Use good names for functions and variables : “You should name a variable using the same care with which you name a first-born child.”, Robert C. Martin, Clean Code: A Handbook of Agile Software Craftsmanship.

    A bit more concretely, this means:

    The length of a variable name should be proportional to its scope. In a list comprehension or short loop, i might be an acceptable name for the running variable, but variables that are used at many different places should have descriptive names.

    The name of variables should reflect the content or meaning of the variable and not only the type. Names like dict_list would not have been a good name for the constraints.

    Function names should contain a verb. Moreover, the length of a function name is typically inversely proportional to its scope. The public functions like maximize and minimize can have very short names. At a lower level of abstraction you typically need more words to describe what a function does.

  • Never import a private function in another module : By following this strictly, you can be sure that you can rename or refactor private functions without looking at other modules. Of course it is also not a solution to copy paste the function! If you would like to import a function that starts with an underscore, rename it.

  • All functions have a Google style docstring : The docstring describes all arguments and outputs. For arrays, please document how many dimensions and what shape they have. Look around in the code to find examples if you are in doubt. Example:

    def ordered_logit(formula, data, dashboard=False):
        """Estimate an ordered probit model with maximum likelihood.
            formula (str): A patsy formula.
            data (str): A pandas DataFrame.
            dashboard (bool): Switch on the dashboard.
            res: optimization result.

    In particular each docstring should start with a one liner that describes very concisely what the function does. The one liner should be in imperative mode, i.e. not “This function does” …” , but “Do …” and end with a period.

  • Unit tests. : If you write a small helper whose interface might change during refactoring, it is sufficient if the function that calls it is tested. But all functions that are exposed to the user must have unit tests.

  • PEP8 compliant and black formatted (we check this automatically). : We make this such a hard requirement because it’s boring and we don’t want to bother about it in code reviews. Not because we think that all PEP8 compliant code is automatically good. Watch this video if you haven’t seen it yet.

  • Use pathlib for all file paths operations. : You can find the pathlib documentation here

  • Object serialization. : Pickling and unpickling of DataFrames should be done with pd.read_pickle and pd.to_pickle.

  • We prefer a functional style over object oriented programming. : Unless you have very good reasons for writing a class, we prefer you don’t do it. You might want to watch this

  • Don’t use global variables unless absolutely necessary : Exceptions are global variables from a config file that replace magic numbers. Never use mutable global variables!

Styleguide for the documentation#

  • General. : The documentation is rendered with Sphinx and written in Markedly Structured Text. How-to guides are usually Jupyter notebooks.

  • Purpose of documents. : Our documentation is inspired by the system developed by Daniele Procida.

    • How-to guides are problem-oriented and show how to achieved specific tasks.

    • Explanations contain information on theoretical concepts underlying estimagic, such as numerical differentiation and moment-based estimation.

    • The API Reference section contains auto-generated API reference documentation and provides additional details about the implementation.

  • Headings. : Only the first letter of a title is capitalized.

  • Format. : The code formatting in .md files is ensured by blacken-docs.