{* ../../docs_src/query_params_str_validations/tutorial003.py hl[9] *}

## Ajouter des validations par expressions régulières

On peut définir une <abbr title="Une expression régulière, regex ou regexp est une suite de caractères qui définit un pattern de correspondance pour les chaînes de caractères.">expression régulière</abbr> à laquelle le paramètre doit correspondre :

import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;
import java.lang.reflect.Method;
import java.util.ArrayDeque;
import java.util.Collection;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;

import com.google.common.util.concurrent.ExecutionError;
import com.google.common.util.concurrent.UncheckedExecutionException;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.lang.reflect.InvocationTargetException;
import java.nio.charset.UnsupportedCharsetException;
import java.util.ConcurrentModificationException;
import java.util.NoSuchElementException;
import java.util.concurrent.CancellationException;

import java.time.LocalDateTime;
import java.time.ZoneId;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.codelibs.core.misc.Pair;
import org.codelibs.fess.es.log.bsbhv.BsSearchLogBhv;

	}

	if ctx.MemLimit > 0 {
		debug.SetMemoryLimit(int64(ctx.MemLimit))
	}

	// Do not use RLIMIT_AS as that is not useful and at times on systems < 4Gi
	// this can crash the Go runtime if the value is smaller refer
	// - https://github.com/golang/go/issues/38010
	// - https://github.com/golang/go/issues/43699
	// So do not add `sys.SetMaxMemoryLimit()` this is not useful for any practical purposes.
	return nil

etcd is a distributed key value store that provides a reliable way to store data across a cluster of machines.

## Get started

### 1. Prerequisites

- Docker 18.03 or above, refer here for [installation](https://docs.docker.com/install/).

### 2. Start etcd

etcd uses [gcr.io/etcd-development/etcd](https://console.cloud.google.com/gcr/images/etcd-development/GLOBAL/etcd) as a primary container registry.

        "includeAll": false,
        "multi": false,
        "name": "datasource",
        "options": [],
        "query": "prometheus",
        "queryValue": "",
        "refresh": 1,
        "regex": "",
        "skipUrlSync": false,
        "type": "datasource"
      },
      {
        "current": {
          "selected": true,
          "text": "default",
          "value": "default"

    val agentNum: Int
        get() {
            if (System.getenv().containsKey("USERNAME")) {
                val agentNumEnv = System.getenv("USERNAME").replaceFirst("tcagent", "")
                if (Regex("""\d+""").containsMatchIn(agentNumEnv)) {
                    return agentNumEnv.toInt()
                }
            }
            return 1
        }

But whenever you need them and go and learn them, know that you can already use them directly in **FastAPI**.

### 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 | Python 3.10+ Pydantic v1

```Python hl_lines="11"

import com.google.common.collect.testing.MinimalCollection;
import com.google.common.collect.testing.features.CollectionFeature;
import com.google.common.collect.testing.features.CollectionSize;
import java.lang.reflect.Method;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.junit.Ignore;

/**