"value": "$__all"
        },
        "label": "Data source",
        "name": "DS_PROMETHEUS",
        "options": [],
        "query": "prometheus",
        "refresh": 1,
        "regex": "",
        "type": "datasource"
      },
      {
        "current": {},
        "datasource": {
          "type": "prometheus",
          "uid": "${DS_PROMETHEUS}"
        },

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

### Pydantic v1 `regex` instead of `pattern` { #pydantic-v1-regex-instead-of-pattern }

Before Pydantic version 2 and before FastAPI 0.100.0, the parameter was called `regex` instead of `pattern`, but it's now deprecated.

You could still see some code using it:

//// tab | Pydantic v1

      while (true) {
        val line = source.readUtf8Line() ?: break
        if (line.isEmpty() || line.startsWith("#")) continue

        var i = 0
        val parts = line.split(Regex(" ")).toTypedArray()

        val element = WebPlatformUrlTestData()
        element.input = unescape(parts[i++])

        val base = if (i < parts.size) parts[i++] else null
        element.base =
          when {

import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

import org.apache.commons.lang3.time.DurationFormatUtils;
import org.apache.commons.text.StringEscapeUtils;
import org.apache.logging.log4j.LogManager;

        assertFalse(urlFilter.match("https://other.com/page.html"));
    }

    /**
     * Test adding invalid regex include pattern
     */
    public void test_addInclude_invalidRegex() {
        String sessionId = "test-session-004";
        urlFilter.init(sessionId);

        // Invalid regex pattern should be handled gracefully
        urlFilter.addInclude(".*[invalid");

package okhttp3

import assertk.assertThat
import assertk.assertions.matches
import org.junit.jupiter.api.Test

class OkHttpTest {
  @Test
  fun testVersion() {
    assertThat(OkHttp.VERSION).matches(Regex("[0-9]+\\.[0-9]+\\.[0-9]+(-.+)?"))
  }

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Utility class for parsing CSV text
 */
public final class KuromojiCSVUtil {
    private static final char QUOTE = '"';

    private static final char COMMA = ',';

  companion object {
    private const val TOKEN = "([a-zA-Z0-9-!#$%&'*+.^_`{|}~]+)"
    private const val QUOTED = "\"([^\"]*)\""
    private val TYPE_SUBTYPE = Regex("$TOKEN/$TOKEN")
    private val PARAMETER = Regex(";\\s*(?:$TOKEN=(?:$TOKEN|$QUOTED))?")

    /**
     * Returns a media type for this string.
     *
     * @throws IllegalArgumentException if this is not a well-formed media type.
     */

import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.util.regex.MatchResult;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Preconditions;
import java.io.File;
import java.io.FilenameFilter;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

/**
 * File name filter that only accepts files matching a regular expression. This class is thread-safe
 * and immutable.
 *
 * @author Apple Chow
 * @since 1.0
 */