Getdefault

Getdefault is an informal name for a class of functions or methods that retrieve a value while supplying a fallback default when the requested value is absent. The pattern appears across programming languages and libraries under various names such as get, getOrDefault, get_default, or get_default_value; some APIs use a distinct setdefault to also insert the default into the data structure.

Typical behavior is: check for a value associated with a key or parameter; if present, return it; otherwise return a supplied or preconfigured default. Implementations differ in whether they mutate state (for example, setdefault in some collections inserts the default) and how they treat explicit nulls or sentinel values. Some frameworks provide argument-level defaults (e.g., command-line parsers), configuration systems return defaults when settings are missing, and map or dictionary types offer convenience methods to avoid boilerplate existence checks.

Common examples include dictionary lookups with fallback, argument-parsing libraries that expose a get_default method, and collection APIs like Java’s Map.getOrDefault. Language-level features such as default function parameters and null-coalescing operators serve a similar role by providing fallback values succinctly.

Best practices encourage documenting defaults, choosing explicit defaults that preserve invariants, and avoiding surprising side effects (such as unintentionally populating collections). Consideration should also be given to immutability, performance when computing defaults lazily, and security implications of using sensitive defaults.