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docs/validation.md

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+# Validation
+
+Redis OM uses [Pydantic](pydantic-url) behind the scenes to validate data at runtime, based on the model's type annotations.
+
+## Basic Type Validation
+
+Validation works for basic type annotations like `str`. Thus, given the following model:
+
+```python
+class Customer(HashModel):
+    first_name: str
+    last_name: str
+    email: EmailStr
+    join_date: datetime.date
+    age: int
+    bio: Optional[str]
+```
+
+... Redis OM will ensure that `first_name` is always a string.
+
+But every Redis OM model is also a Pydantic model, so you can use existing Pydantic validators like `EmailStr`, `Pattern`, and many more for complex validation!
+
+## Complex Validation
+
+Let's see what happens if we try to create a `Customer` object with an invalid email address.
+
+```python
+# We'll get a validation error if we try to use an invalid email address!
+Customer(
+    first_name="Andrew",
+    last_name="Brookins",
+    email="Not an email address!",
+    join_date=datetime.date.today(),
+    age=38,
+    bio="Python developer, works at Redis, Inc."
+)
+```
+
+This code generates the following error:
+
+```
+ Traceback:
+ pydantic.error_wrappers.ValidationError: 1 validation error for Customer
+ email
+   value is not a valid email address (type=value_error.email)
+```
+
+We'll also get a validation error if we change a field on a model instance to an invalid value and then try to save it:
+
+```python
+andrew = Customer(
+    first_name="Andrew",
+    last_name="Brookins",
+    email="andrew.brookins@example.com",
+    join_date=datetime.date.today(),
+    age=38,
+    bio="Python developer, works at Redis, Inc."
+)
+
+andrew.email = "Not valid"
+andrew.save()
+```
+
+Once again, we get the valiation error:
+
+```
+ Traceback:
+ pydantic.error_wrappers.ValidationError: 1 validation error for Customer
+ email
+   value is not a valid email address (type=value_error.email)
+```