Conditional Writes

Dynantic provides an SQLModel-like DSL for conditional operations on DynamoDB.

Basic Conditions

from dynantic import Attr

# Create-if-not-exists
user = User(user_id="u1", email="test@example.com")
user.save(condition=User.email.not_exists())

# Optimistic locking
user.save(condition=User.version == 5)

# Conditional delete
User.delete("u1", condition=(User.balance == 0) & (User.status == "inactive"))

Complex Conditions

# Combine multiple conditions
condition = (User.age >= 18) & (User.status == "active") & ~User.is_banned.exists()
user.save(condition=condition)

# Dynamic field names with Attr()
User.delete("u1", condition=Attr("legacy_field").not_exists())

Comparison Operators

Operator	Example
==, !=	User.status == "active"
<, <=, >, >=	User.age >= 18
.exists()	User.email.exists()
.not_exists()	User.deleted_at.not_exists()
.begins_with(prefix)	User.name.begins_with("A")
.contains(value)	User.tags.contains("premium")
.between(low, high)	User.age.between(18, 65)
.is_in([values])	User.status.is_in(["active", "pending"])

Logical Operators

Operator	Meaning	Example
&	AND	(User.age >= 18) & (User.active == True)
\|	OR	(User.role == "admin") \| (User.role == "super")
~	NOT	~User.is_banned.exists()

Use Attr() for mypy compatibility

The metaclass DSL (User.status == "active") works at runtime but mypy doesn't understand it. Use Attr("status") == "active" for type-safe code.