Jinja Reserved Keywords

Overview

​ 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.​

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List of Reserved Keywords

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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 ​

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Common Error: JSON Serialization Issue

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Error:

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

Solution:

​ 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. ​

Example:

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

{{CTX.customers.data["items"]}}

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

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Best Practices

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• 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. ​

Conclusion

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