How can the "in" filter of FastAPI be utilized with values that have commas?

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If you want to use the "in" filter of FastAPI with values that have commas, you can pass them as a list. For example, if you want to filter a list of products based on their categories, and some categories have commas in their names, you can pass the list of categories as a list of strings, like this:

from typing import List
from fastapi import FastAPI, Query

app = FastAPI()

@app.get("/products/")
async def get_products(categories: List[str] = Query(None, alias="category__in")):
    # assume products is a list of products with a "category" field
    if categories:
        selected_products = [p for p in products if p.category in categories]
    else:
        selected_products = products
    return {"products": selected_products}

In this example, the alias parameter is used to rename the category__in parameter to categories for easier readability. The List[str] type indicates that the parameter accepts a list of strings. When a request is made with multiple categories, they should be passed as a comma-separated list in the query string, like this:

GET /products/?categories=electronics,clothing,household

This will return all products that have a category that is either "electronics", "clothing", or "household". If a category has a comma in its name (e.g. "kitchen, cookware"), it should be passed as a separate string element in the list:

GET /products/?categories=electronics,kitchen, cookware,clothing