- Choice of erasure set size is automatic based on the number of drives available, let's say for example if there are 32 servers and 32 drives which is a total of 1024 drives. In this scenario 16 becomes the erasure set size. This is decided based on the greatest common divisor (GCD) of acceptable erasure set sizes ranging from *4 to 16*.

Now you know that whenever you need them you can use them in **FastAPI**.

## Default values { #default-values }

You can, of course, use default values other than `None`.

Let's say that you want to declare the `q` query parameter to have a `min_length` of `3`, and to have a default value of `"fixedquery"`:

{* ../../docs_src/query_params_str_validations/tutorial005_an_py39.py hl[9] *}

/// note

And it can also be used by yourself, to debug, check and test the same application.

## The `password` flow { #the-password-flow }

Now let's go back a bit and understand what is all that.

The `password` "flow" is one of the ways ("flows") defined in OAuth2, to handle security and authentication.

OAuth2 was designed so that the backend or API could be independent of the server that authenticates the user.

You can add custom exception handlers with <a href="https://www.starlette.dev/exceptions/" class="external-link" target="_blank">the same exception utilities from Starlette</a>.

Let's say you have a custom exception `UnicornException` that you (or a library you use) might `raise`.

And you want to handle this exception globally with FastAPI.

You could add a custom exception handler with `@app.exception_handler()`:

	}
	if got, want := fh2.ModifiedDate, fh.ModifiedDate; got != want {
		t.Errorf("ModifiedDate: got %d, want %d\n", got, want)
	}

	if sysfh, ok := fi.Sys().(*FileHeader); !ok && sysfh != fh {
		t.Errorf("Sys didn't return original *FileHeader")
	}
}

func TestFileHeaderRoundTrip(t *testing.T) {
	fh := &FileHeader{
		Name:             "foo.txt",
		UncompressedSize: 987654321,

        «««
        Erstelle eine [virtuelle Umgebung](../virtual-environments.md#create-a-virtual-environment){.internal-link target=_blank}
        »»»

    Good translation (German) – URL stays like in the English source.

        «««
        Erstelle eine [Virtuelle Umgebung](../virtual-environments.md){.internal-link target=_blank}
        »»»


### HTML abbr elements

	resp, err := getSysServicesRPC.Call(ctx, client.gridConn(), grid.NewMSS())
	return resp.ValueOrZero(), err
}

// GetSysConfig - fetch sys config for a remote node.
func (client *peerRESTClient) GetSysConfig(ctx context.Context) (info madmin.SysConfig, err error) {
	sent := time.Now()
	resp, err := getSysConfigRPC.Call(ctx, client.gridConn(), grid.NewMSS())

{* ../../docs_src/sql_databases/tutorial002_an_py310.py ln[83:93] hl[83:84,88:89] *}

### Delete a Hero Again { #delete-a-hero-again }

**Deleting** a hero stays pretty much the same.

We won't satisfy the desire to refactor everything in this one. 😅

{* ../../docs_src/sql_databases/tutorial002_an_py310.py ln[96:103] hl[101] *}

### Run the App Again { #run-the-app-again }

	// Run tests
	for _, tt := range testCases {
		t.Run(tt.name, func(t *testing.T) {
			if tt.expired {
				// Expired already.
				pp.SetExpires(UTCNow().AddDate(0, 0, -10))
			} else {
				// Expires in 10 days.
				pp.SetExpires(UTCNow().AddDate(0, 0, 10))
			}

			tt.fv.Set("Policy", base64.StdEncoding.EncodeToString([]byte(pp.String())))

For example, let's say you have 4 API endpoints (*path operations*):

* `/items/public/`
* `/items/private/`
* `/users/{user_id}/activate`
* `/items/pro/`