@Marvin In prefect 3, how do I reference custom blocks in my flow

In Prefect 3.x, blocks are a powerful feature used for managing configuration storage, infrastructure, and secrets within your flows. They help package and manage configurations for interacting with external systems such as databases, cloud storage, and other online services. To reference and use custom blocks in your flow, you should follow these steps: 1. Define the Block: Blocks can be defined as Python classes that wrap around the functionality you need. These blocks can store configuration details or leverage APIs for interactions. 2. Instantiate and Save the Block: Once defined, you can instantiate a block with the necessary configuration and save it for use later. Saving a block is akin to committing that configuration or state into your Prefect environment. Example:

python
   from prefect.blocks.core import Block

   class Cube(Block):
       edge_length_inches: float

       def get_surface_area(self):
           return 6 * self.edge_length_inches ** 2

   rubiks_cube = Cube(edge_length_inches=2.25)
   rubiks_cube.save("rubiks-cube")

3. Load and Use the Block: In your flow, you can load a previously saved block by its name and use its methods or properties. Example:

python
   from prefect import flow

   @flow
   def calculate_cube_surface_area(cube_name):
       cube = Cube.load(cube_name)
       print(cube.get_surface_area())

   if __name__ == "__main__":
       calculate_cube_surface_area("rubiks-cube")

4. Accessing Blocks: Blocks can be accessed and managed through the Prefect dashboard or through the command line interface (CLI). Use

prefect block type ls

to see available block types, or navigate through the UI to manage blocks. Blocks provide a structured way to manage configurations that can be shared across different flow runs or deployments, making it more manageable to maintain and alter configurations centrally without modifying the actual flow code. For further reading on blocks in Prefect 3.x, you can check the Prefect documentation on blocks.

@Marvin I'm getting an Nameerror that Cube is not defined. Any ideas?

The

NameError

you're encountering typically indicates that the class

Cube

has not been defined or imported in your current script. Here are some steps to resolve this issue: 1. Check Definition: Ensure that the

Cube

class is defined in your script before it's used. If it's defined in a different module or script, you need to import it properly. 2. Import Correctly: If

Cube

is defined in another file, make sure you're importing it correctly. For instance, if

Cube

is defined in a file called

my_blocks.py

, you should import it using:

python
   from my_blocks import Cube

3. Check Spelling and Casing: Make sure that the name

Cube

is spelled and cased correctly wherever it's defined and used. 4. Class Definition: Verify that the class is defined as follows:

python
   from prefect.blocks.core import Block

   class Cube(Block):
       edge_length_inches: float

       def get_surface_area(self):
           return 6 * self.edge_length_inches ** 2

5. Run in the Appropriate Context: Ensure that the piece of code using

Cube

is within the same file or executed in a context where

Cube

is available (such as an interactive session where it has been defined). If the problem persists, double-check the module organizational structure to verify that all definitions and imports are correctly set up. Let me know if you need further assistance or if any other issues arise!