# pydantic_core._pydantic_core.ValidationError: 1 validation error for Order
items
  Input should be a valid list [type=list_type, input_value='item1,item2', input_type=str]

- **ID:** `python/pydantic-validation-error-list-type`
- **Domain:** python
- **Category:** type_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

A comma-separated string was passed to a list-typed field. Pydantic v2 does not split strings into lists automatically.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 2.x | active | — | — |

## Workarounds

1. **** (96% success)
   ```
   data['items'] = 'item1,item2'.split(',')
   ```
2. **** (94% success)
   ```
   from pydantic import BaseModel, field_validator

class Order(BaseModel):
    items: list[str]

    @field_validator('items', mode='before')
    @classmethod
    def split_items(cls, v):
        if isinstance(v, str):
            return v.split(',')
        return v
   ```

## Dead Ends

- **** — list() on a string iterates characters, producing ['i','t','e','m','1',',',...]. (98% fail)
- **** — Security risk and fails because 'item1,item2' is not valid Python syntax for a list. (99% fail)