애플리케이션이나 웹 API를 만들 때, 모든 것을 하나의 파일에 담을 수 있는 경우는 드뭅니다.

**FastAPI**는 모든 유연성을 유지하면서도 애플리케이션을 구조화할 수 있게 해주는 편리한 도구를 제공합니다.

/// info | 정보

Flask를 사용해 보셨다면, 이는 Flask의 Blueprints에 해당하는 개념입니다.

///

## 예시 파일 구조 { #an-example-file-structure }

다음과 같은 파일 구조가 있다고 해봅시다:

```
.
├── app
│   ├── __init__.py
│   ├── main.py
│   ├── dependencies.py
│   └── routers
│   │   ├── __init__.py
│   │   ├── items.py

            # parameter might sometimes be a path parameter and sometimes not. See
            # `tests/test_infer_param_optionality.py` for an example.
            field_info = params.Path(annotation=use_annotation)
        elif is_uploadfile_or_nonable_uploadfile_annotation(
            type_annotation
        ) or is_uploadfile_sequence_annotation(type_annotation):

   * changes the contents of the transposed table and vice versa.
   *
   * <p>The returned table supports update operations as long as the input table supports the
   * analogous operation with swapped rows and columns. For example, in a {@link HashBasedTable}
   * instance, {@code rowKeySet().iterator()} supports {@code remove()} but {@code
   * columnKeySet().iterator()} doesn't. With a transposed {@link HashBasedTable}, it's the other
   * way around.

   * they will be absent (unless they were already returned).
   *
   * If there are I/O problems during iteration, this iterator fails silently. For example, if the
   * hosting filesystem becomes unreachable, the iterator will omit elements rather than throwing
   * exceptions.
   *

    if (supportsRemove) {
      // We use a copy of "entryToRemove" in the assertion because "entryToRemove" might be
      // invalidated and have undefined behavior after entrySet.removeAll(entriesToRemove),
      // for example entryToRemove.getValue() might be null.
      Entry<K, V> entryToRemoveCopy = mapEntry(entryToRemove.getKey(), entryToRemove.getValue());

      int initialSize = map.size();

   * semantics of builder can be arbitrarily complex. Still, a factory class can be created in the
   * test to facilitate equality testing. For example:
   *
   * <pre>
   * public class FooTest {
   *
   *   private static final class FooFactoryForTest {
   *     public static Foo create(String a, String b, int c, boolean d) {
   *       return Foo.builder()

pkg syscall (windows-386), type ProcessEntry32 struct
pkg syscall (windows-386), type ProcessEntry32 struct, DefaultHeapID uintptr
pkg syscall (windows-386), type ProcessEntry32 struct, ExeFile [260]uint16
pkg syscall (windows-386), type ProcessEntry32 struct, Flags uint32
pkg syscall (windows-386), type ProcessEntry32 struct, ModuleID uint32
pkg syscall (windows-386), type ProcessEntry32 struct, ParentProcessID uint32

   * {@code ClassCastException} for any elements {@code e1} and {@code e2} in the multiset. If the
   * user attempts to add an element to the multiset that violates this constraint (for example, the
   * user attempts to add a string element to a set whose elements are integers), the {@code
   * add(Object)} call will throw a {@code ClassCastException}.
   *

                    if (pointer instanceof Lifecycle.DependenciesPointer) {
                        // For dependencies: ensure current project's phase starts after dependency's phase completes
                        // Example: project's compile starts after dependency's package completes
                        // TODO: String scope = ((Lifecycle.DependenciesPointer) pointer).scope();
                        projects.get(project)

它们处在某种意义上的“对立端”，彼此互补。

Requests 设计非常简单直观，易于使用，且有合理的默认值。同时它也非常强大、可定制。

这就是为什么，正如其官网所说：

> Requests 是有史以来下载量最高的 Python 包之一

它的用法非常简单。例如，进行一次 `GET` 请求，你会这样写：

```Python
response = requests.get("http://example.com/some/url")
```

对应地，FastAPI 的 API 路径操作可能看起来是这样的：

```Python hl_lines="1"
@app.get("/some/url")
def read_url():
    return {"message": "Hello World"}
```