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If, Elif, and Else let you conditionally render different components based on expression results. They mirror Python’s own if/elif/else syntax and read the same way — no wrappers, no extra indentation.

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Basic Usage

The simplest case: show something only when a condition is true. Toggle the switch to see the alert appear and disappear. A lone If renders its children when the condition is truthy, and renders nothing when it’s falsy.

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If / Else

Add an Else branch to render fallback content when the condition is false. Toggle the switch to see the two branches swap.

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If / Elif / Else

Chain multiple conditions with Elif. The renderer evaluates them in order and renders the first match. If nothing matches, the Else branch renders. Use the select below to change the status and watch the right badge appear. Select “Error” or “Something else” to see different branches render. The Else catches anything that doesn’t match the explicit conditions.

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Conditions Are Expressions

The first argument to If and Elif is a reactive expression. With Rx, you can use Python operators directly:
Any expression the language supports — comparisons, boolean logic, pipes — works as a condition.

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Chain Rules

Consecutive If/Elif/Else siblings in the same parent form a single conditional chain:
  • A chain starts with If and extends through consecutive Elif and Else siblings
  • Elif and Else are optional — a lone If is valid
  • Else must be last in a chain
  • Any non-conditional sibling breaks the chain — including another If, which starts a new independent chain
This produces three independent Condition nodes with a Text between the first and second.

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Wire Format

In the Python DSL, you write natural If/Elif/Else siblings. During serialization, these are grouped into a single Condition node on the wire. The If and Elif components never appear in the JSON directly — they’re purely authoring constructs. Each Elif becomes a case entry with a when expression. The Else branch becomes the else field. See the Condition protocol reference for the full schema.

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API Reference

If

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str
required
Expression to evaluate. Renders children when truthy. Can be passed as a positional argument.

Elif

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str
required
Expression to evaluate. Must follow an If or another Elif. Can be passed as a positional argument.

Else

Renders children when no preceding If or Elif matched. Takes no condition argument.

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Protocol Reference

For the wire format schema, see the Condition protocol definition.