> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/fastapi/fastapi/llms.txt
> Use this file to discover all available pages before exploring further.

# Path

> API reference for the FastAPI Path parameter function

# Path

Declare a path parameter for a path operation. Path parameters are always required and are extracted from the URL path.

```python theme={null}
from typing import Annotated
from fastapi import FastAPI, Path

app = FastAPI()

@app.get("/items/{item_id}")
async def read_items(
    item_id: Annotated[int, Path(title="The ID of the item to get")],
):
    return {"item_id": item_id}
```

## Signature

```python theme={null}
def Path(
    default: Any = ...,
    *,
    alias: str | None = None,
    title: str | None = None,
    description: str | None = None,
    gt: float | None = None,
    ge: float | None = None,
    lt: float | None = None,
    le: float | None = None,
    min_length: int | None = None,
    max_length: int | None = None,
    pattern: str | None = None,
    examples: list[Any] | None = None,
    deprecated: bool | str | None = None,
    include_in_schema: bool = True,
    json_schema_extra: dict[str, Any] | None = None,
) -> Any
```

## Parameters

<ParamField path="default" type="Any" default="...">
  Default value if the parameter field is not set. This doesn't affect Path parameters as the value is always required. The parameter is available only for compatibility.
</ParamField>

<ParamField path="alias" type="str | None" default="None">
  An alternative name for the parameter field. This will be used to extract the data and for the generated OpenAPI. Particularly useful when you can't use the name you want because it is a Python reserved keyword.
</ParamField>

<ParamField path="title" type="str | None" default="None">
  Human-readable title for the parameter.
</ParamField>

<ParamField path="description" type="str | None" default="None">
  Human-readable description for the parameter.
</ParamField>

<ParamField path="gt" type="float | None" default="None">
  Greater than validation. If set, the value must be greater than this. Only applicable to numbers.
</ParamField>

<ParamField path="ge" type="float | None" default="None">
  Greater than or equal validation. If set, the value must be greater than or equal to this. Only applicable to numbers.
</ParamField>

<ParamField path="lt" type="float | None" default="None">
  Less than validation. If set, the value must be less than this. Only applicable to numbers.
</ParamField>

<ParamField path="le" type="float | None" default="None">
  Less than or equal validation. If set, the value must be less than or equal to this. Only applicable to numbers.
</ParamField>

<ParamField path="min_length" type="int | None" default="None">
  Minimum length for strings.
</ParamField>

<ParamField path="max_length" type="int | None" default="None">
  Maximum length for strings.
</ParamField>

<ParamField path="pattern" type="str | None" default="None">
  RegEx pattern for strings.
</ParamField>

<ParamField path="discriminator" type="str | None" default="None">
  Parameter field name for discriminating the type in a tagged union.
</ParamField>

<ParamField path="strict" type="bool | None" default="None">
  If True, strict validation is applied to the field.
</ParamField>

<ParamField path="multiple_of" type="float | None" default="None">
  Value must be a multiple of this. Only applicable to numbers.
</ParamField>

<ParamField path="allow_inf_nan" type="bool | None" default="None">
  Allow `inf`, `-inf`, `nan`. Only applicable to numbers.
</ParamField>

<ParamField path="max_digits" type="int | None" default="None">
  Maximum number of allowed digits for numbers.
</ParamField>

<ParamField path="decimal_places" type="int | None" default="None">
  Maximum number of decimal places allowed for numbers.
</ParamField>

<ParamField path="examples" type="list[Any] | None" default="None">
  Example values for this field.
</ParamField>

<ParamField path="deprecated" type="bool | str | None" default="None">
  Mark this parameter field as deprecated. It will affect the generated OpenAPI (visible at `/docs`).
</ParamField>

<ParamField path="include_in_schema" type="bool" default="True">
  Whether to include this parameter field in the generated OpenAPI.
</ParamField>

<ParamField path="json_schema_extra" type="dict[str, Any] | None" default="None">
  Any additional JSON schema data.
</ParamField>

## Examples

### Basic Path Parameter

```python theme={null}
from typing import Annotated
from fastapi import FastAPI, Path

app = FastAPI()

@app.get("/items/{item_id}")
async def read_item(item_id: Annotated[int, Path()]):
    return {"item_id": item_id}
```

### Path Parameter with Metadata

```python theme={null}
@app.get("/items/{item_id}")
async def read_item(
    item_id: Annotated[int, Path(title="Item ID", description="The ID of the item to retrieve")]
):
    return {"item_id": item_id}
```

### Numeric Validations

```python theme={null}
@app.get("/items/{item_id}")
async def read_item(
    item_id: Annotated[int, Path(gt=0, le=1000)]
):
    return {"item_id": item_id}
```

<Note>
  The `item_id` must be greater than 0 and less than or equal to 1000.
</Note>

### String Validations

```python theme={null}
@app.get("/users/{username}")
async def read_user(
    username: Annotated[str, Path(min_length=3, max_length=20, pattern="^[a-zA-Z0-9_]+$")]
):
    return {"username": username}
```

<Note>
  The `username` must be between 3 and 20 characters and can only contain alphanumeric characters and underscores.
</Note>

## Important Notes

<Warning>
  Path parameters are always required. You cannot make them optional or provide default values.
</Warning>

<Note>
  Path parameters are extracted from the URL path template defined in the route decorator (e.g., `/items/{item_id}`).
</Note>