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.

But we want to be able to parameterize that fixed content.

You send it a token and it returns an authenticated user.

This provider might be charging you per request, and calling it might take some extra time than if you had a fixed mock user for tests.

You probably want to test the external provider once, but not necessarily call it for every test that runs.

**FastAPI** is already being used in production in many applications and systems. And the test coverage is kept at 100%. But its development is still moving quickly.

New features are added frequently, bugs are fixed regularly, and the code is still continuously improving.

Several of these are explored in the next chapters of the tutorial.

## Order matters { #order-matters }

When creating *path operations*, you can find situations where you have a fixed path.

Like `/users/me`, let's say that it's to get data about the current user.

And then you can also have a path `/users/{user_id}` to get data about a specific user by some user ID.

* Data <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>
* Data validation
* Automatic documentation

## Defaults { #defaults }

As query parameters are not a fixed part of a path, they can be optional and can have default values.

In the example above they have default values of `skip=0` and `limit=10`.

So, going to the URL:

```
http://127.0.0.1:8000/items/
```

        this.loadLines()
        if (!options.noInit) this.init()
    }

    loadLines() {
        // Load all the lines and create the container so that the size is fixed
        // Otherwise it would be changing and the user viewport would be constantly
        // moving as she/he scrolls
        const finish = this.generateFinish()
        finish.style.visibility = 'hidden'

     */
    public byte[] generateNonce() {
        final byte[] nonce = new byte[isGCMCipher() ? 16 : 12];

        if (isGCMCipher()) {
            // SMB 3.1.1 GCM: 96-bit random/fixed + 32-bit counter for guaranteed uniqueness
            // Fill first 12 bytes with random data
            secureRandom.nextBytes(nonce);

            // Last 4 bytes: incrementing counter for guaranteed uniqueness

* The `password`.
* An optional `scope` field as a big string, composed of strings separated by spaces.
* An optional `grant_type`.

/// tip

The OAuth2 spec actually *requires* a field `grant_type` with a fixed value of `password`, but `OAuth2PasswordRequestForm` doesn't enforce it.

If you need to enforce it, use `OAuth2PasswordRequestFormStrict` instead of `OAuth2PasswordRequestForm`.

///

        CountDownLatch startLatch = new CountDownLatch(1);
        CountDownLatch endLatch = new CountDownLatch(threadCount);

        // Use AtomicLong to simulate the fixed bytesEncrypted field
        AtomicLong mockBytesEncrypted = new AtomicLong(0);
        AtomicLong totalTime = new AtomicLong(0);
        AtomicInteger operations = new AtomicInteger(0);

     */
    private byte[] createValidNegotiateResponseBuffer() {
        byte[] buffer = createBasicNegotiateResponseBuffer();

        // Add a small security buffer at a safe offset (after the fixed structure)
        SMBUtil.writeInt2(64, buffer, 56); // Security buffer offset (relative to header start)
        SMBUtil.writeInt2(8, buffer, 58); // Security buffer length