n -= len(src)
	}
	b.write0(src[0:n])
}

var (
	newline = []byte{'\n'}
	tabs    = []byte("\t\t\t\t\t\t\t\t")
)

func (b *Writer) writePadding(textw, cellw int, useTabs bool) {
	if b.padbytes[0] == '\t' || useTabs {
		// padding is done with tabs
		if b.tabwidth == 0 {
			return // tabs have no width - can't do any padding
		}
		// make cellw the smallest multiple of b.tabwidth

The patterns used by [ServeMux] now allow one or more spaces or tabs after the method name.

	}
	return "", 0, false
}

func parseAttrValueSpec(p *parseState, s string, i int) (string, int, bool) {
	// “An attribute value specification consists of
	// optional spaces, tabs, and up to one line ending,
	// a = character,
	// optional spaces, tabs, and up to one line ending,
	// and an attribute value.”
	i = skipSpace(s, i)
	if i+1 < len(s) && s[i] == '=' {
		i = skipSpace(s, i+1)
		if _, j, ok := parseAttrValue(s, i); ok {

    ```Python hl_lines="81-83"
    {!> ../../../docs_src/websockets/tutorial003.py!}
    ```

Zum Ausprobieren:

* Öffnen Sie die Anwendung mit mehreren Browser-Tabs.
* Schreiben Sie Nachrichten in den Tabs.
* Schließen Sie dann einen der Tabs.

Das wird die Ausnahme `WebSocketDisconnect` auslösen und alle anderen Clients erhalten eine Nachricht wie:

```
Client #1596980209979 left the chat
```

		if p.HeadingIDs {
			// Parse and remove ID attribute.
			// It must come before trailing '#'s to more closely follow the spec:
			//    The optional closing sequence of #s must be preceded by spaces or tabs
			//    and may be followed by spaces or tabs only.
			// But Goldmark allows it to come after.
			id, s = extractID(p, s)

			// Goldmark is strict about the id syntax.
			for _, c := range id {
				if c >= 0x80 || !isLetterDigit(byte(c)) {

            return assertOutput('Standard error', matcher)
        }

        private HtmlTestClassExecutionResult assertOutput(heading, Matcher<? super String> matcher) {
            def tabs = html.select("div.tab")
            def tab = tabs.find { it.select("h2").text() == heading }
            assert matcher.matches(tab ? TextUtil.normaliseLineSeparators(tab.select("span > pre").first().textNodes().first().wholeText) : "")

Then open 10 tabs at <a href="http://127.0.0.1:8000/docs#/default/read_slow_users_slowusers__get" class="external-link" target="_blank">http://127.0.0.1:8000/docs#/default/read_slow_users_slowusers__get</a> at the same time.

Go to the *path operation* "Get `/slowusers/`" in all of the tabs. Use the "Try it out" button and execute the request in each tab, one right after the other.

=== "Python 3.8+"

    ```Python hl_lines="81-83"
    {!> ../../../docs_src/websockets/tutorial003.py!}
    ```

To try it out:

* Open the app with several browser tabs.
* Write messages from them.
* Then close one of the tabs.

That will raise the `WebSocketDisconnect` exception, and all the other clients will receive a message like:

```
Client #1596980209979 left the chat
```

!!! tip

	start := i
	for start > 0 && (s[start-1] == ' ' || s[start-1] == '\t') {
		start--
	}
	end := i + 1
	for end < len(s) && (s[end] == ' ' || s[end] == '\t') {
		end++
	}
	// TODO: Do tabs count? That would be a mess.
	if i >= 2 && s[i-1] == ' ' && s[i-2] == ' ' {
		return &HardBreak{}, start, end, true
	}
	return &SoftBreak{}, start, end, true

// removed, if there were any. Otherwise, the input is returned unchanged.
//
// The base64 decoder already skips newline characters, so we don't need to
// filter them out here.
func removeSpacesAndTabs(data []byte) []byte {
	if !bytes.ContainsAny(data, " \t") {
		// Fast path; most base64 data within PEM contains newlines, but
		// no spaces nor tabs. Skip the extra alloc and work.
		return data