What inspired **FastAPI**, how it compares to alternatives and what it learned from them.

## Intro { #intro }

**FastAPI** wouldn't exist if not for the previous work of others.

There have been many tools created before that have helped inspire its creation.

I have been avoiding the creation of a new framework for several years. First I tried to solve all the features covered by **FastAPI** using many different frameworks, plug-ins, and tools.

Bug reports
-----------

import java.lang.reflect.Method;
import java.util.Locale;
import junit.framework.TestCase;

/**
 * Since annotations have some reusability issues that force copy and paste all over the place, it's
 * worth having a test to ensure that all our Feature enums have their annotations correctly set up.
 *
 * @author George van den Driessche
 */
public class FeatureEnumTest extends TestCase {

			wantErr: "Invalid according to Policy: Policy Condition failed: [eq, $bucket, testbucket]. FormValues have multiple values: [testbucket, anotherbucket]",
		},
		{
			name: "XAmzSignature does not have to appear in policy",
			fv:   defaultFormVals.Clone().Set(xhttp.AmzSignature, "my-signature"),
		},
		{
			name: "XIgnoreFoo does not have to appear in policy",
			fv:   defaultFormVals.Clone().Set("X-Ignore-Foo", "my-foo-value"),
		},

        // When/Then - All error codes should have high bit set (0xC prefix)
        for (int status : errorStatuses) {
            assertTrue((status & (int) 0xC0000000L) == (int) 0xC0000000L,
                    "Error status should have severity bits set to 0xC: " + Integer.toHexString(status));
        }
    }

    @Test
    @DisplayName("Should have status codes array")
    void testStatusCodesArray() {

# Cookie Parameter Models { #cookie-parameter-models }

If you have a group of **cookies** that are related, you can create a **Pydantic model** to declare them. 🍪

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

/// tip

/// warning

Have in mind that as the Pydantic team no longer supports Pydantic v1 in recent versions of Python, starting from Python 3.14, using `pydantic.v1` is also not supported in Python 3.14 and above.

///

### Pydantic v1 and v2 on the same app { #pydantic-v1-and-v2-on-the-same-app }

      @CompatibleWith("C") @Nullable Object columnKey);

  // Views

  /**
   * Returns a view of all mappings that have the given row key. For each row key / column key /
   * value mapping in the table with that row key, the returned map associates the column key with
   * the value. If no mappings in the table have the provided row key, an empty map is returned.
   *

## Parameterized dependencies { #parameterized-dependencies }

All the dependencies we have seen are a fixed function or class.

But there could be cases where you want to be able to set parameters on the dependency, without having to declare many different functions or classes.

Let's imagine that we want to have a dependency that checks if the query parameter `q` contains some fixed content.

Let's say you have a file structure as described in [Bigger Applications](bigger-applications.md):

```
.
├── app
│   ├── __init__.py
│   └── main.py
```

In the file `main.py` you have your **FastAPI** app:


{* ../../docs_src/app_testing/app_a_py310/main.py *}

### Testing file { #testing-file }