## 🗄 `Field`

🥇, 👆 ✔️ 🗄 ⚫️:

//// tab | 🐍 3️⃣.6️⃣ & 🔛

```Python hl_lines="4"
{!> ../../docs_src/body_fields/tutorial001.py!}
```

////

//// tab | 🐍 3️⃣.1️⃣0️⃣ & 🔛

```Python hl_lines="2"
{!> ../../docs_src/body_fields/tutorial001_py310.py!}
```

////

/// warning

## Import `Field`

First, you have to import it:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[4] *}


/// warning

Notice that `Field` is imported directly from `pydantic`, not from `fastapi` as are all the rest (`Query`, `Path`, `Body`, etc).

///

## Declare model attributes

You can then use `Field` with model attributes:

          <type>String</type>
          <required>true</required>
        </field>
        <field>
          <version>1.0.0</version>
          <name>configuration</name>
          <description>The place and syntax used to change the value of this expression.</description>
          <type>String</type>
        </field>
        <field>
          <version>1.0.0</version>
          <name>cliOptions</name>

index.field.anchor=anchor
index.field.segment=segment
index.field.role=role
index.field.boost=boost
index.field.created=created
index.field.timestamp=timestamp
index.field.label=label
index.field.mimetype=mimetype
index.field.parent_id=parent_id
index.field.important_content=important_content
index.field.content=content
index.field.content_minhash_bits=content_minhash_bits
index.field.cache=cache

  // The only valid values for this field are 'Apply' and 'Update'.
  optional string operation = 2;

  // APIVersion defines the version of this resource that this field set
  // applies to. The format is "group/version" just like the top-level
  // APIVersion field. It is necessary to track the version of a field
  // set because it cannot be automatically converted.

            <p>Since Maven 3.2.4, the type for this field has been changed to Properties to match the de-facto
            format.
            <p>Each toolchain defines its own properties names and semantics.
          </description>
        </field>
        <field>
          <name>configuration</name>
          <version>1.0.0+</version>
          <type>DOM</type>

	var field []byte
	_ = field
	var zb0001 uint32
	zb0001, err = dc.ReadMapHeader()
	if err != nil {
		err = msgp.WrapError(err)
		return
	}
	for zb0001 > 0 {
		zb0001--
		field, err = dc.ReadMapKeyPtr()
		if err != nil {
			err = msgp.WrapError(err)
			return
		}
		switch msgp.UnsafeString(field) {
		default:
			err = dc.Skip()
			if err != nil {

				tx.AddError(rel.Field.Set(tx.Statement.Context, reflectValue.Index(i), reflect.MakeSlice(rel.Field.IndirectFieldType, 0, 10).Interface()))
			default:
				tx.AddError(rel.Field.Set(tx.Statement.Context, reflectValue.Index(i), reflect.New(rel.Field.FieldType).Interface()))
			}
		}
	}

	for i := 0; i < reflectResults.Len(); i++ {
		elem := reflectResults.Index(i)
		for idx, field := range relForeignFields {

func (z *TierConfigMgr) DecodeMsg(dc *msgp.Reader) (err error) {
	var field []byte
	_ = field
	var zb0001 uint32
	zb0001, err = dc.ReadMapHeader()
	if err != nil {
		err = msgp.WrapError(err)
		return
	}
	for zb0001 > 0 {
		zb0001--
		field, err = dc.ReadMapKeyPtr()
		if err != nil {
			err = msgp.WrapError(err)
			return
		}
		switch msgp.UnsafeString(field) {
		case "Tiers":
			var zb0002 uint32

///

/// tip | "提示"

注意，模型属性的类型、默认值及 `Field` 的代码结构与*路径操作函数*的参数相同，只不过是用 `Field` 替换了`Path`、`Query`、`Body`。

///

## 添加更多信息

`Field`、`Query`、`Body` 等对象里可以声明更多信息，并且 JSON Schema 中也会集成这些信息。

*声明示例*一章中将详细介绍添加更多信息的知识。

## 小结

Pydantic 的 `Field` 可以为模型属性声明更多校验和元数据。