coding-patterns

Coding Patterns

Based on the fastai style guide and Jeremy's 3 decades of coding experience, and used across all of his projects, not only fastai ones.

Use the fastcore/fasthtml ecosystem (fastcore, fasthtml, fastlite, ...) when picking libraries - these are Jeremy's own, editable-installed as siblings, and preferred over heavier third-party alternatives.

Every Construct Must Earn Its Place

Readers assume everything present is necessary. When they see str(x) on something that's already a str, they stop and wonder what subtle thing it's guarding against; when the answer is "nothing", they paid for a mystery with no payoff. The same goes for defensive copies (list(x) that's never mutated), "just in case" try/excepts, redundant type coercions, and unused parameters. Before adding any construct, know why it's needed; if you can't say, leave it out. The cost doubles in nbdev projects, where tests are documentation.

The same applies to prose in code: almost never add comments (only when the code is truly unclear), and don't add type hints, docstrings, or boilerplate that pull no weight. Prefer concise, readable code over verbose "enterprise" style.

Docments

Docments are trailing comments on function parameters that fastcore uses for documentation. A signature with docments (or any long signature) uses this layout: ( stays on the def line, each parameter on its own line indented 4, and ): alone on its own line at def indent:

@delegates(start_kernel)
async def run_kernel(
    kernel_name='python3', # Kernelspec name to launch
    manager_cls=KernelManager, # Manager class, e.g. a subclass customizing launch
    **kwargs
):

NEVER remove docments when refactoring - they're essential documentation.

When **kwargs passes through to a known callee, decorate with @delegates(callee) so the signature shows the real options - and delegates REQUIRES the collector to be named kwargs, not kw etc. Skip the decorator when the callee's own signature is just **kwargs (nothing to delegate).