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145 lines
4.5 KiB
Plaintext
145 lines
4.5 KiB
Plaintext
---
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title: Loop
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---
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## What is Loop Node?
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A **Loop** node executes repetitive tasks that depend on previous iteration results until exit conditions are met or the maximum loop count is reached.
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## Loop vs. Iteration
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<table>
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<thead>
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<tr>
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<th>Type</th>
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<th>Dependencies</th>
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<th>Use Cases</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td><strong>Loop</strong></td>
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<td>Each iteration depends on previous results</td>
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<td>Recursive operations, optimization problems</td>
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</tr>
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<tr>
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<td><strong>Iteration</strong></td>
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<td>Iterations execute independently</td>
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<td>Batch processing, parallel data handling</td>
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</tr>
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</tbody>
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</table>
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## Configurations
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<table>
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<thead>
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<tr>
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<th>Parameter</th>
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<th>Description</th>
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<th>Example</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>Loop Termination Condition</td>
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<td>Expression that determines when to exit the loop</td>
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<td><code>x < 50</code>, <code>error_rate < 0.01</code></td>
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</tr>
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<tr>
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<td>Maximum Loop Count</td>
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<td>Upper limit on iterations to prevent infinite loops</td>
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<td>10, 100, 1000</td>
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</tr>
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<tr>
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<td>Loop Variables</td>
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<td>Values that persist across iterations and remain accessible to nodes after the loop completes</td>
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<td>A counter <code>x < 50</code> increases by 1 each iteration. Use it for calculations inside the loop, then access its final value in later workflow steps.</td>
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</tr>
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<tr>
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<td>Exit Loop Node</td>
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<td>Immediately ends the loop when reached</td>
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<td>Caps execution at 10 iterations, regardless of other conditions.</td>
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</tr>
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</tbody>
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</table>
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<Info>
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The loop can be terminated by either the **Exit Loop Node** or the **Loop Termination Condition**. When either condition is met, the loop will immediately exit.
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If no exit conditions are specified, the loop will continue executing (similar to `while (true)`) until it reaches the **Maximum Loop Count**.
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</Info>
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## Example 1: Basic Loop
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**Goal: Generate random numbers between 1-100 until getting a number less than 50.**
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**Steps**:
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1. Set up a **Loop** node by configuring its **Loop Termination Condition** to trigger when the **Template** node returns `done`.
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2. Set up a **Code** node that generates random integers between `1` and `100`.
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3. Set up an **IF/ELSE** node with the following logic:
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- For numbers ≥ 50: Output the `Current Number` and continue the loop
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- For numbers < 50: Output the `Final Number`, and then use the **Template** node to return `done`
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4. The workflow terminates automatically once a number below `50` is generated.
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## Example 2: Advanced Loop (with Variables and Exit Node)
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**Goal: Design a workflow that generates a poem through four iterative refinements, with each version building upon the previous one.**
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**Steps:**
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1. Set up a **Loop** node with those **Loop Variables**:
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- num: A counter starting at 0, incrementing by 1 per iteration
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- verse: A text variable initialized with `I haven't started creating yet`
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2. Set up an **IF/ELSE** node that evaluates the iteration count:
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- When num > 3: Proceed the **Exit Loop** node
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- When num ≤ 3: Proceed to the **LLM** node
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3. Set up an **LLM** node to generate poems.
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<Info>
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Example Prompt:
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You are a European literary figure who can create poetic verses based on `sys.query`.
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`verse` is your last creation. You can progress based on your previous work.
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</Info>
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The first iteration begins with the initial verse value `I haven't started creating yet`. Each subsequent iteration builds upon the previous output, with the new poem replacing the verse variable’s content.
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4. Set up a **Variable Assigner** node to manage state:
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- Increment num by 1 after each iteration
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- Update verse with the newly generated poem
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5. When executed, the workflow will produce four versions of your poem, each iteration building upon its previous output.
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<video controls src="https://assets-docs.dify.ai/2025/04/7ecfc04458aa38e721baaa5f6355486c.mp4" width="100%"></video>
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{/*
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Contributing Section
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DO NOT edit this section!
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It will be automatically generated by the script.
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*/}
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---
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[Edit this page](https://github.com/langgenius/dify-docs/edit/main/en/guides/workflow/node/loop.mdx) | [Report an issue](https://github.com/langgenius/dify-docs/issues/new?template=docs.yml)
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