Loops and Iteration

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Overview

• Repeat sections of your prompt for each item in a list.
• Access each item’s index for numbered output or additional logic.
• Handle empty lists gracefully using the else clause.

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Syntax

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Basic Loop

{{ for item in list }}
  - {{ item }}
{{ endfor }}

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Loop with Index

{{ for item, index in list }}
  {{ index }}: {{ item }}
{{ endfor }}

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Loop with else

{{ for item in list }}
  - {{ item }}
{{ else }}
  No items to display.
{{ endfor }}

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Examples

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Basic Example: Listing Items

{{ for fruit in ["apple", "banana", "cherry"] }}
  - {{ fruit }}
{{ endfor }}

- apple
- banana
- cherry

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Example with Index

{{ for fruit, index in ["apple", "banana", "cherry"] }}
  {{ index + 1 }}. {{ fruit }}
{{ endfor }}

1. apple
2. banana
3. cherry

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Handling Empty Lists

{{ for item in [] }}
  - {{ item }}
{{ else }}
  The list is empty. No items to display.
{{ endfor }}

The list is empty. No items to display.

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Advanced Usage

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Iterating Over Objects

{{ for user in users }}
  - Name: {{ user.name }}, Age: {{ user.age }}
{{ endfor }}

users = [
  { name: "Alice", age: 30 },
  { name: "Bob", age: 25 }
]

- Name: Alice, Age: 30
- Name: Bob, Age: 25

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Nested Loops

{{ for group, groupIndex in groups }}
  Group {{ groupIndex + 1 }}:
  {{ for member in group.members }}
    - {{ member }}
  {{ endfor }}
{{ endfor }}

groups = [
  { members: ["Alice", "Bob"] },
  { members: ["Charlie", "Dana"] }
]

Group 1:
  - Alice
  - Bob
Group 2:
  - Charlie
  - Dana

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Best Practices

1. Keep Loops Simple:
   • Avoid deeply nested loops unless necessary. Complex loops can make your prompts harder to read and maintain.
2. Use Default Values:
   • Provide defaults for variables to prevent errors when lists are empty or data is incomplete.
   • Example: {{ item || "Unknown" }}
3. Combine with Conditionals:
   • Use if statements inside loops for conditional logic.
   {{ for user in users }}
     {{ if user.active }}
       - {{ user.name }} (Active)
     {{ else }}
       - {{ user.name }} (Inactive)
     {{ endif }}
   {{ endfor }}
   
4. Debugging:
   • Temporarily output the list and its elements to ensure the loop is iterating as expected.

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Debugging Tips

• Verify Data: Print the list you’re iterating over to ensure it contains the expected data.
• Check Syntax: Ensure endfor is present and properly matched with for.
• Use else for Debugging: Add an else clause to confirm whether the list is empty.

{{ for item in list }}
  - {{ item }}
{{ else }}
  Debug: The list is empty or not defined.
{{ endfor }}

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Summary

Ready for more dynamic control? Explore Conditional Statements to complement your loops.