# Replace None

This function block provides a simple fallback mechanism: when the primary input is missing (`None`), it outputs a user-provided replacement value so downstream blocks continue to receive valid data.

## 📥 Inputs <a href="#inputs" id="inputs"></a>

* `Input Data` (Generic) — Primary data to be checked for presence.
* `New Data` (Generic) — Replacement data to use when the primary input is `None`.

## 📤 Outputs <a href="#outputs" id="outputs"></a>

* `Replaced Data` (Generic) — The resulting data: either the original `Input Data` if present, or `New Data` when the input is `None`.

## 🕹️ Controls <a href="#controls" id="controls"></a>

This block has no interactive controls.

## 🎯 Features <a href="#features" id="features"></a>

* Minimal, reliable fallback for missing values to prevent breaks in a flow.
* Generic data type support — works with images, numbers, text, lists, or other data types.
* Lightweight and deterministic behavior — always passes either the original or the replacement value.

## 📝 Usage Instructions <a href="#usage" id="usage"></a>

1. Connect the source you want to guard to `Input Data`.
2. Provide a default or fallback value to `New Data`. This can be a static value, a previously stored value, or a placeholder image/number/text.
3. Read the result from `Replaced Data` and continue the pipeline as usual.

Example uses: provide a placeholder image when a camera feed briefly fails, supply a default number for calculations, or pass a backup string when a network response is missing.

## ⚙️ How it runs <a href="#evaluation" id="evaluation"></a>

When the flow runs, this block checks whether `Input Data` is present. If it is present, that value is forwarded. If it is `None`, the block forwards the value supplied to `New Data`. If both are `None`, the output will be `None` (so ensure a meaningful fallback is provided when needed).

## 💡 Tips and Tricks <a href="#tips-and-tricks" id="tips-and-tricks"></a>

* Combine with `Is None` to create branching logic (for example, trigger an alert only when the original input is missing).
* Use with `Data Memory` to freeze and re-use the last valid value as the `New Data` fallback.
* When dealing with image streams (e.g., from `Camera USB` or `Stream Reader`), feed a representative static image into `New Data` so viewers like `Show Image` always have something meaningful to display.
* Pair with `Debug Input` or `Data to JSON` to log when fallbacks are used, helping you monitor data quality over time.
* For saving fallback events or results, link `Replaced Data` to `CSV Export` or `Image Logger` depending on data type.

## 🛠️ Troubleshooting <a href="#troubleshooting" id="troubleshooting"></a>

* If you still see `None` at the output, confirm a non-`None` value is provided to either `Input Data` or `New Data`.
* For image pipelines: if the fallback appears but looks wrong, check the format (color channels, size) of the `New Data` to match downstream expectations.