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Input Variable Handling

The pl.run() function handles input variables in the following ways:

1. Normal Usage:

Provide all required variables as defined in your prompt template:

response = pl.run(
   prompt_name="movie_recommender",
   prompt_release_label="prod",
   input_variables={
       "favorite_movie": "The Shawshank Redemption"
   },
)

2. Missing Variables:

If you don’t provide the required input variables, you’ll receive a warning in the console, but the prompt template will still run. The missing variables will be sent to the LLM as unprocessed strings:

response = pl.run(
   prompt_name="movie_recommender",
   prompt_release_label="prod",
   input_variables={},
)

WARNING: While getting your prompt template: Some input variables are missing: (`favorite_movie`)
Undefined variable in message index 1: 'favorite_movie' is undefined

3. Extra Variables:

If you include extra variables that aren’t in the template, they will be ignored:

response = pl.run(
   prompt_name="movie_recommender",
   prompt_release_label="prod",
   input_variables={
       "favorite_movie": "The Shawshank Redemption",
       "release_year": 1994
   },
)

In this case, the release_year variable will be ignored in the LLM request if it’s not part of the current template.

When you need to add new input variables to your prompt template, it’s important to keep your source code in sync with the template changes. This guide outlines the process for deploying these updates to your production environment.

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Example Scenario

Assume you have a prompt template version tagged with prod that uses only one input variable, favorite_movie:

response = pl.run(
    prompt_name="movie_recommender",
    prompt_release_label="prod",
    input_variables={
        "favorite_movie": "The Shawshank Redemption"
    },
)

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Update Process

Follow these steps to safely add a new mood variable to your prompt template:

1. Create a new template version with the new mood variable

2. Apply a unique temporary label (e.g., new-var) to the new version

3. Update and deploy your code to use the new template version and include the new variable:

response = pl.run(
   prompt_name="movie_recommender",
   prompt_release_label="new-var",
   input_variables={
       "favorite_movie": "The Shawshank Redemption",
       "mood": "uplifting"
   },
)

4. In the PromptLayer UI, move the prod label to the most recent prompt version

5. Update your source code to reference the prod prompt version again and deploy:

response = pl.run(
   prompt_name="movie_recommender",
   prompt_release_label="prod",
   input_variables={
       "favorite_movie": "The Shawshank Redemption",
       "mood": "uplifting"
   },
)

6. Delete the temporary new-var label from the PromptLayer UI