Understand how to use pydantic extra, allow, and forbid

python_fundamentals/exercises/pydantic-extra.py

@@ -0,0 +1,87 @@
+from typing import ClassVar
+
+from pydantic import BaseModel, ConfigDict, Field, ValidationError
+
+
+class WeatherAPI(BaseModel):
+    model_config: ClassVar[ConfigDict] = ConfigDict(extra="ignore")
+    air_quality: int
+    city: str
+
+
+class BankAccount(BaseModel):
+    model_config: ClassVar[ConfigDict] = ConfigDict(extra="forbid")
+    account_number: str = Field(
+        min_length=12,
+        max_length=12,
+    )
+    account_type: str
+
+
+class EventLog(BaseModel):
+    model_config: ClassVar[ConfigDict] = ConfigDict(extra="allow")
+    event_id: int
+    event_type: str
+
+
+"""
+BaseModel defines `model_config` as a class-level configuration.
+
+Annotating it with `ClassVar[ConfigDict]`
+tells static type checkers that this attribute
+belongs to the class rather than individual instances.
+"""
+
+
+if __name__ == "__main__":
+    print("=" * 60)
+    print("EventLog (extra='allow')")
+    print("=" * 60)
+
+    try:
+        event = EventLog(
+            event_id=0,
+            event_type="Error",
+            event_description="ValidationError",
+        )
+
+        print(event.model_dump())
+
+    except ValidationError as exc:
+        print(exc)
+
+    print()
+
+    print("=" * 60)
+    print("WeatherAPI (extra='ignore')")
+    print("=" * 60)
+
+    try:
+        pune_weather = WeatherAPI(
+            city="Pune",
+            air_quality=10,
+            humidity="low",  # type: ignore
+        )
+
+        print(pune_weather.model_dump())
+
+    except ValidationError as exc:
+        print(exc)
+
+    print()
+
+    print("=" * 60)
+    print("BankAccount (extra='forbid')")
+    print("=" * 60)
+
+    try:
+        bank_account = BankAccount(
+            account_number="123456789012",
+            account_type="Savings",
+            is_admin=True,  # type: ignore
+        )
+
+        print(bank_account.model_dump())
+
+    except ValidationError as exc:
+        print(exc)