Default value
A default value is a predefined or automatically supplied value used when an expected input, argument, field, or configuration setting is omitted or unspecified.
Python How-To
A default value is a value automatically used for a function parameter when the corresponding argument is not explicitly supplied.
- How it is used
- Makes common Python function and constructor calls shorter while allowing callers to override the usual value.
- How deep it goes
- Works through function evolution, default evaluation, shared mutable objects, and the `None` remedy, then applies ordering rules to data classes.
- Examples
- Uses task completion, list sorting, shared task lists, dictionary lookups, and a bill data class.
- What you can do after
- Build it from scratch: define convenient Python defaults and avoid unintended state sharing across calls.
Essential TypeScript 5, Third Edition
A default parameter is a function parameter with an initializer used when the caller omits the argument or supplies undefined.
- How it is used
- Supplies a fallback for omitted function arguments so calls can use fewer arguments than the function declares.
- How deep it goes
- Works through syntax, calls, outputs, and parameter-order constraints in JavaScript and TypeScript, without detailing initializer evaluation order.
- Examples
- Uses a tax calculation, a price-summing function, and a product-discount function to show fallback values in calls.
- What you can do after
- Practice/perform defining fallback parameters in JavaScript or TypeScript functions and checking that the fallback does not mask other argument problems.
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The Well-Grounded Rubyist, Fourth Edition
A default argument is a method parameter with a value assigned when the caller does not supply that argument.
- How it is used
- Makes Ruby method arguments optional by providing values when callers omit them.
- How deep it goes
- Works through omitted and supplied arguments, mixed-parameter binding, and keyword defaults; stops short of evaluating default expressions.
- Examples
- Uses method calls with omitted or overriding arguments, a mixed signature, and calls supplying selected keyword arguments.
- What you can do after
- Build it from scratch: define Ruby methods with optional positional or keyword parameters and predict how calls bind their arguments.
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API Design Patterns
A default value is a value automatically selected when an API request or data field does not specify an explicit value.
- How it is used
- Guides API designers in representing omitted choices across fields, serialization, resource retrieval, and partial updates.
- How deep it goes
- Compares Boolean, numeric, string, list, and field-mask strategies, stopping short of detailed serialization implementation.
- Examples
- Uses omitted names, empty strings, numeric zero, chat-room permissions, empty lists, and default field masks as concrete cases.
- What you can do after
- Build it from scratch by selecting explicit, predictable default representations and documenting exceptions for API consumers.
The Well-Grounded Python Developer: How the pros use Python and Flask
A default value is a value automatically assigned to a function parameter when the caller does not provide that parameter.
- How it is used
- Makes common function calls shorter while allowing callers to override optional behavior.
- How deep it goes
- Explains omitted arguments, keyword overrides, and parameter ordering, but does not examine default-evaluation internals.
- Examples
- Uses print() options and a full_name function with optional middle and last names.
- What you can do after
- Practice/perform it by defining optional Python parameters and overriding named options when calling a function.
Get Programming with JavaScript Next: New features of ECMAScript 2015, 2016, and beyond
A function parameter form that supplies an automatic fallback value when the caller does not provide an argument or provides undefined.
- How it is used
- Provides fallback values for expected function arguments while allowing callers to supply alternatives.
- How deep it goes
- Works through dependent expressions, invocation-time context, positional behavior, and avoiding repeated computation; it does not develop a general argument-shifting mechanism.
- Examples
- Uses approval-rating charts, a changing AJAX host, a one-argument range call, and shared ratings calculations.
- What you can do after
- Build it from scratch: write function defaults that depend on earlier parameters and pass precomputed values to skip redundant work.
Python Workout: 50 ten-minute exercises
A function parameter that has a predefined value when the caller omits it.
- How it is used
- Uses defaults to make functions accept useful omissions while retaining predictable, fixed parameter roles.
- How deep it goes
- Explains defaults through complete calls and contrasts them with *args, but stops short of implementation internals.
- Examples
- Demonstrates greetings, XML generation with optional content, and summation with an optional starting point.
- What you can do after
- Build it from scratch in Python by defining optional values and choosing defaults instead of accepting arbitrary arguments.
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Kotlin in Action, 2E
A default parameter is a function parameter with a value automatically supplied when the caller omits that argument.
- How it is used
- Reduces overloaded function declarations and makes calls with optional configuration concise and readable.
- How deep it goes
- Explains declaration syntax, positional and named calls, function-type defaults, recompilation behavior, and Java overload generation.
- Examples
- Uses joinToString formatting options, a default transform lambda, and a Person age default in an introductory collection example.
- What you can do after
- Apply it in Kotlin to replace routine overloads and design callable APIs with optional positional, named, or function-valued arguments.
Python Workout, Second Edition
A default parameter is a function parameter that receives a specified fallback value when no argument is supplied.
- How it is used
- Handles optional function inputs while providing flexible, reusable interfaces.
- How deep it goes
- Explains fallback calls, parameter ordering, function argument counts, and mutable-default reuse, but stops short of implementation internals beyond __code__.
- Examples
- Uses greeting calls and an XML-building function with optional content and keyword attributes.
- What you can do after
- Apply it via Python function definitions to support omitted arguments and known optional values.
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React in Depth
A default property value is the value assigned to a component property when the caller does not provide one.
- How it is used
- Supplies predictable component behavior when callers omit optional properties.
- How deep it goes
- Explains destructuring and defaultProps with precedence rules, but does not descend into runtime implementation internals.
- Examples
- Uses MenuItem target, Greeting name, and Car hasSunroof to illustrate fallback values and optional properties.
- What you can do after
- Apply it via destructuring or defaultProps, while avoiding duplicate fallback declarations and separating defaults from requiredness.
React Quickly, Second Edition
A default property value is a value assigned when an object property is absent or unspecified during destructuring.
- How it is used
- Simplifies component interfaces by supplying ordinary JavaScript fallbacks during property destructuring.
- How deep it goes
- Defines syntax, ordering practice, and UI examples, but stops short of language internals.
- Examples
- Demonstrates menu link targets, uncontrolled input initialization, and context fallback values.
- What you can do after
- Apply it via destructured component parameters, uncontrolled inputs, and createContext fallbacks.
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Pro ASP.NET Core 7, Tenth Edition
A default value is a value assigned to a route segment variable when the corresponding URL segment is absent.
- How it is used
- Supplies a route segment variable when its URL segment is absent, allowing one route to match more URLs.
- How deep it goes
- Defines the equals-sign syntax and tests matching URLs; does not explain routing internals.
- Examples
- Tests `/capital` for `France`, `/capital/uk` for `uk`, and an overlong path for no match.
- What you can do after
- Operate/configure an ASP.NET Core route to accept an omitted segment while assigning its variable a specified value.
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ASP.NET Core in Action, 3e
A default parameter value is a value specified in a method signature that is supplied when an argument is omitted.
- How it is used
- Uses route defaults to provide shorter URLs and handler defaults to supply values for omitted bound arguments.
- How deep it goes
- Explains route matching, assigned route values, parameter placement, and handler signatures, but does not develop broader binding internals.
- Examples
- Uses product URLs, route-value tables, and a stock handler with int id = 0.
- What you can do after
- Apply it via ASP.NET Core route templates and endpoint-handler signatures to accept omitted URL or argument values.
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The Design of Web APIs, Second Edition
A default value is a parameter value applied when an API consumer does not provide that parameter.
- How it is used
- Minimizes API input by letting implementations infer omitted values in bodies, query parameters, and headers.
- How deep it goes
- Defines server-inferred values and JSON Schema defaults, stopping short of detailed implementation mechanics.
- Examples
- Uses money transfers, currency, recurring dates, pagination limits, and transaction-list metadata as concrete examples.
- What you can do after
- Apply it via API schemas and response metadata to reduce inputs and reveal the values actually used.
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The Quick Python Book, Fourth Edition
A default parameter value is a value assigned to a function parameter and used when the corresponding argument is omitted from a call.
- How it is used
- Uses defaults to shorten common function calls and configure complex functions through optional keyword-named settings.
- How deep it goes
- Explains declaration, positional ordering, keyword overrides, and mutable-object reuse, but stops short of implementation beyond compilation-time assignment.
- Examples
- Demonstrates exponentiation, named power arguments, optional file metadata, and an accumulating list default.
- What you can do after
- Apply it by defining optional parameters, overriding defaults positionally or by name, and detecting mutable-default side effects.
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Modern C, Third Edition
A default argument is a value supplied automatically when a caller omits an otherwise optional function argument.
- How it is used
- Provides optional arguments for C function interfaces through function-like macros.
- How deep it goes
- Explains dispatch, default insertion, function wrapping, and excess-argument errors, but stops short of general language-level defaults.
- Examples
- Demonstrates strtod and strtoul wrappers, DEFAULT1 expansions, and CALL3 substitution traces.
- What you can do after
- Apply it via C preprocessor macros to wrap functions with omitted arguments and compile-time arity checking.
Practical Automation with PowerShell: Effective scripting from the console to the cloud
A default value is a predefined value supplied when an input is not provided or cannot be determined.
- How it is used
- Guides parameter and form design by supplying safe values when users omit optional inputs.
- How deep it goes
- Explains when to use defaults and how they fit parameter classification, but stops short of implementation syntax.
- Examples
- Uses Hyper-V storage paths, SharePoint time zones, derived site URLs, and template lookups as concrete applications.
- What you can do after
- Configure automation inputs by selecting defaults, permitting overrides, and deriving values users should not enter manually.
The Joy of JavaScript
A function parameter that takes a predefined value when no argument is supplied.
- How it is used
- Uses default parameters to establish initial state while refactoring iterative code into recursive, composable functions.
- How deep it goes
- Explains syntax through a worked recursive example, but does not develop broader parameter-evaluation semantics.
- Examples
- Uses computeCipher with default i and hash parameters to initialize recursive hash computation.
- What you can do after
- Build it from scratch by defining recursive functions whose parameters carry explicit initial state.
Learn PowerShell in a Month of Lunches: Fourth Edition, Covers Windows, Linux, and macOS
A default parameter value is an input automatically supplied to a command parameter when the caller does not provide one.
- How it is used
- Uses fallback inputs to make administrative scripts convenient while preserving optional control over computer names and filters.
- How deep it goes
- Explains declarations, omitted arguments, session defaults, script blocks, and scope, but stops short of deeper parameter validation.
- Examples
- Demonstrates disk inventory parameters, localhost and drive-type fallbacks, credential defaults, and credential-prompting script blocks.
- What you can do after
- Apply default values in PowerShell scripts and configure command-specific or session-wide defaults through $PSDefaultParameterValues.
Grokking Relational Database Design
A DEFAULT constraint supplies a specified value for a column when an inserted row omits that column.
- How it is used
- Uses column defaults to fill omitted inserted values, especially timestamps, numeric fields, and optional placeholders.
- How deep it goes
- Explains purpose, use cases, SQL placement, CURRENT_TIMESTAMP, and the limit that DEFAULT does not block NULL.
- Examples
- Demonstrates purchase_time DEFAULT CURRENT_TIMESTAMP in a purchase table and discusses timestamp, numeric, and placeholder defaults.
- What you can do after
- Apply it via SQL by adding DEFAULT values to column definitions and combining them with NOT NULL when NULL is unacceptable.
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Related concepts
- inputconfigures · An input is a value, information, or signal supplied to a system, computation, or interface for processing or to influence its behavior.
- function overloadingalternative to · Function overloading is defining multiple callable operations with the same name but different parameter signatures, with behavior selected according to the call.
- listcontrasts with · A list is an ordered collection of elements arranged in a sequence.
- JSON Schemaused by · JSON Schema is a standard vocabulary and specification for describing, validating, and annotating the structure and constraints of JSON data.
- optional function argumentalternative to · An optional function argument is an input corresponding to a parameter that a caller is not required to supply because omission is permitted by the function's interface.
- validate-only fieldconfigures · A validate-only field is a request field that causes an operation to validate its inputs without applying the requested state change.
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