Dynamic variables are resolved at runtime, allowing you to use current date, time, and other values without hardcoding them.
Built-in Variables
| Variable | Example Output | Description |
|---|
{{today}} | January 19, 2026 | Human-readable date |
{{date}} | 2026-01-19 | ISO date format |
{{now}} | 2026-01-19T11:00:00 | ISO datetime |
{{timestamp}} | 1737280800 | Unix timestamp |
{{uuid}} | a1b2c3d4-… | Random UUID |
{{year}} | 2026 | Current year |
{{month}} | January | Current month name |
Usage in Agent
from praisonaiagents import Agent
# Dynamic variable in prompt
agent = Agent(instructions="You are a news researcher")
result = agent.start("Find AI news for {{today}}")
# Resolves to: "Find AI news for January 19, 2026"
# Dynamic variable in instructions
agent = Agent(
instructions="You research news. Today is {{today}}.",
role="Researcher"
)
result = agent.run("What's new in AI?")
Usage in Workflow YAML
framework: praisonai
topic: "Research AI developments for {{today}}"
roles:
researcher:
role: AI Researcher
goal: "Find news for {{month}} {{year}}"
tasks:
research:
description: "Research {{topic}}"
expected_output: "Summary with sources"
Custom Providers
Register your own dynamic variables:
from praisonaiagents.utils import register_variable_provider
# Simple function
register_variable_provider("author", lambda: "PraisonAI Team")
# Now {{author}} works in any prompt
agent.start("Article by {{author}} on {{today}}")
Dynamic variables are resolved in Agent.start(), Agent.run(), and Workflow execution.
The import is lazy-loaded, so there’s no performance impact if you don’t use them.
API Reference
from praisonaiagents.utils import (
substitute_variables, # Main function
get_provider_registry, # Get the registry
register_variable_provider # Register custom provider
)
# Direct substitution
text = substitute_variables("Hello {{today}}", {})
# Returns: "Hello January 19, 2026"
# With static variables
text = substitute_variables("Topic: {{topic}} Date: {{today}}", {"topic": "AI"})
# Returns: "Topic: AI Date: January 19, 2026"
