# Learn { #learn }

Here are the introductory sections and the tutorials to learn **FastAPI**.

@app.get("/items/valid", response_model=Item)
def get_valid():
    return Item(aliased_name="valid", price=1.0)


@app.get("/items/coerce", response_model=Item)
def get_coerce():
    return Item(aliased_name="coerce", price="1.0")


@app.get("/items/validlist", response_model=list[Item])
def get_validlist():
    return [
        Item(aliased_name="foo"),

    owner_ids: Optional[list[int]] = None


@app.get("/items/valid", response_model=Item)
def get_valid():
    return {"name": "valid", "price": 1.0}


@app.get("/items/coerce", response_model=Item)
def get_coerce():
    return {"name": "coerce", "price": "1.0"}


@app.get("/items/validlist", response_model=list[Item])
def get_validlist():
    return [
        {"name": "foo"},
        {"name": "bar", "price": 1.0},

Now that we have seen how to use `Path` and `Query`, let's see more advanced uses of request body declarations.

## Mix `Path`, `Query` and body parameters { #mix-path-query-and-body-parameters }

First, of course, you can mix `Path`, `Query` and request body parameter declarations freely and **FastAPI** will know what to do.

And you can also declare body parameters as optional, by setting the default to `None`:

          @ParametricNullness E key,
          List<? extends E> list,
          int foundIndex) {
        // Of course, we have to use binary search to find the precise
        // breakpoint...
        int lower = 0;
        int upper = foundIndex;
        // Of course, we have to use binary search to find the precise breakpoint...
        // Everything between lower and upper inclusive compares at <= 0.

@app.get("/items/object", response_model=Item)
def get_object():
    return Item(
        name="object", date=datetime(2021, 7, 26), price=1.0, owner_ids=[1, 2, 3]
    )


@app.get("/items/coerce", response_model=Item)
def get_coerce():
    return {"name": "coerce", "date": datetime(2021, 7, 26).isoformat(), "price": "1.0"}


@app.get("/items/validlist", response_model=list[Item])
def get_validlist():
    return [

  public void testSingleSimpleStats() {
    StatsCounter counter = new SimpleStatsCounter();
    for (int i = 0; i < 11; i++) {
      counter.recordHits(1);
    }
    for (int i = 0; i < 13; i++) {
      counter.recordLoadSuccess(i);
    }
    for (int i = 0; i < 17; i++) {
      counter.recordLoadException(i);
    }
    for (int i = 0; i < 23; i++) {
      counter.recordMisses(1);
    }

platforms/core-runtime/files/                               @gradle/bt-cortex @gradle/dv-integrations-team

# Core automation platform (core/execution)
platforms/core-execution/                                   @gradle/bt-cortex
platforms/core-execution/build-cache/                       @gradle/bt-cortex @gradle/dv-integrations-team

          echo "Database initialized successfully";
          break;
        fi;
        echo "Waiting for database to be ready... ($$counter/12)";
        sleep 5;
        counter=$$(($$counter + 1));
      done;
      # timeout handling
      if [ $$counter -gt 20 ]; then
        echo "Error: Database failed to start within timeout";
        exit 1;
      fi;

      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        builder.add(counter.getAndIncrement());
      }
    },
    ADD_ARRAY {
      @Override
      void doIt(ImmutableDoubleArray.Builder builder, AtomicInteger counter) {
        double[] array = new double[random.nextInt(10)];
        for (int i = 0; i < array.length; i++) {
          array[i] = counter.getAndIncrement();
        }