Jinja Reserved Keywords


​ This document is intended to provide an overview of Jinja's reserved keywords Rewst users will encounter while building their own automations, and addresses a common TypeError issue that users face when conflicts occur.​

List of Reserved Keywords


Control Structures

  • if, elif, else: Conditional statements

  • for: Looping through sequences

  • while: Loop based on a condition

  • try, except, finally: Exception handling

  • with: Context management ​

Variables and Data Types

  • True, False: Boolean values

  • None: Represents null value

  • del: Deletes a variable ​

Functions and Definitions

  • def: Function definition

  • return: Returns a value from a function

  • yield: Produces a generator

  • lambda: Anonymous function

  • class: Defines a class ​

Operators and Keywords

  • and, or, not: Logical operators

  • in, is: Comparison operators

  • raise: Raise an exception

  • assert: Assertion statement

  • break, continue: Loop control

  • pass: Null operation

  • global, nonlocal: Scope specifiers ​

Built-in Methods

  • split: Splits a string into a list

  • items: Returns a list of dictionary's key-value tuple pairs

  • replace: Replaces a string with another string

  • get: Retrieves the value of a dictionary key

  • result, results: Used in Rewst to store outputs. Note that these are not built-in methods, they're used in Rewst as variable named to store outputs and should not cause issues. ​

Imports and Modules

  • import: Importing modules

  • from: Specifies what attributes to import from a module ​

Common Error: JSON Serialization Issue



​ JSON cannot serialize 'builtin_function_or_method': <built-in method items of dict object at 0x7f618cb407c0> ​


​ Ensure that you're not inadvertently referencing a built-in method like items as an object when you actually intend to use its output. Execute the method first before attempting to serialize it to JSON. ​


​ If the output of an API call stores all the items in a key named items, reference it like this: ​


​ This ensures that you're referencing the actual data rather than the built-in items method, thus avoiding the serialization issue.

Best Practices


  • Always prefix your own variables and function names to avoid collision with these reserved words.

  • Use these words in the appropriate context to ensure readability and maintainability. ​


​ Understanding these protected words in Jinja is critical for effective template development. Familiarize yourself with these terms to write better, error-free code.

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