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prefect.utilities.templating

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Functions

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determine_placeholder_type 

determine_placeholder_type(name: str) -> PlaceholderType
Determines the type of a placeholder based on its name. Args:
  • name: The name of the placeholder
Returns:
  • The type of the placeholder

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find_placeholders 

find_placeholders(template: T) -> set[Placeholder]
Finds all placeholders in a template. Args:
  • template: template to discover placeholders in
Returns:
  • A set of all placeholders in the template

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apply_values 

apply_values(template: T, values: dict[str, Any], remove_notset: bool = True, warn_on_notset: bool = False) -> Union[T, type[NotSet]]
Replaces placeholders in a template with values from a supplied dictionary. Will recursively replace placeholders in dictionaries and lists. If a value has no placeholders, it will be returned unchanged. If a template contains only a single placeholder, the placeholder will be fully replaced with the value. If a template contains text before or after a placeholder or there are multiple placeholders, the placeholders will be replaced with the corresponding variable values. If a template contains a placeholder that is not in values, NotSet will be returned to signify that no placeholder replacement occurred. If template is a dictionary that contains a key with a value of NotSet, the key will be removed in the return value unless remove_notset is set to False. Args:
  • template: template to discover and replace values in
  • values: The values to apply to placeholders in the template
  • remove_notset: If True, remove keys with an unset value
  • warn_on_notset: If True, warn when a placeholder is not found in values
Returns:
  • The template with the values applied

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resolve_block_document_references 

resolve_block_document_references(template: T, client: Optional['PrefectClient'] = None, value_transformer: Optional[Callable[[str, Any], Any]] = None) -> Union[T, dict[str, Any]]
Resolve block document references in a template by replacing each reference with its value or the return value of the transformer function if provided. Recursively searches for block document references in dictionaries and lists. Identifies block document references by the as dictionary with the following structure: 
{
    "$ref": {
        "block_document_id": <block_document_id>
    }
}
where <block_document_id> is the ID of the block document to resolve. Once the block document is retrieved from the API, the data of the block document is used to replace the reference.

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Accessing Values:

To access different values in a block document, use dot notation combined with the block document’s prefix, slug, and block name. For a block document with the structure: 
{
    "value": {
        "key": {
            "nested-key": "nested-value"
        },
        "list": [
            {"list-key": "list-value"},
            1,
            2
        ]
    }
}
examples of value resolution are as follows:
  1. Accessing a nested dictionary: Format: prefect.blocks.<block_type_slug>.<block_document_name>.value.key Example: Returns {"nested-key": "nested-value"}
  2. Accessing a specific nested value: Format: prefect.blocks.<block_type_slug>.<block_document_name>.value.key.nested-key Example: Returns "nested-value"
  3. Accessing a list element’s key-value: Format: prefect.blocks.<block_type_slug>.<block_document_name>.value.list[0].list-key Example: Returns "list-value"

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Default Resolution for System Blocks:

For system blocks, which only contain a value attribute, this attribute is resolved by default. Args:
  • template: The template to resolve block documents in
  • value_transformer: A function that takes the block placeholder and the block value and returns replacement text for the template
Returns:
  • The template with block documents resolved

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resolve_variables 

resolve_variables(template: T, client: Optional['PrefectClient'] = None) -> T
Resolve variables in a template by replacing each variable placeholder with the value of the variable. Recursively searches for variable placeholders in dictionaries and lists. Strips variable placeholders if the variable is not found. Args:
  • template: The template to resolve variables in
Returns:
  • The template with variables resolved

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Classes

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PlaceholderType

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Placeholder