## 情境管理器 { #context-managers }

### 什麼是「情境管理器」 { #what-are-context-managers }

「情境管理器」是那些你可以在 `with` 陳述式中使用的 Python 物件。

例如，[你可以用 `with` 來讀取檔案](https://docs.python.org/3/tutorial/inputoutput.html#reading-and-writing-files)：

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

在底層，`open("./somefile.txt")` 會建立一個稱為「情境管理器」的物件。

# don't exit if this fails ${MC} rm -r --force myminio/$BUCKET set -e ; # reset `e` as active else echo "Bucket '$BUCKET' does not exist, skipping purge." fi fi # Create the bucket if it does not exist if ! checkBucketExists $BUCKET ; then echo "Creating bucket '$BUCKET'" ${MC} mb myminio/$BUCKET else echo "Bucket '$BUCKET' already exists." fi # set versioning for bucket if [ ! -z $VERSIONING ] ; then if [ $VERSIONING = true ] ; then echo "Enabling versioning for '$BUCKET'" ${MC} version enable myminio/$BUCKET...

# don't exit if this fails ${MC} rm -r --force myminio/$BUCKET set -e ; # reset `e` as active else echo "Bucket '$BUCKET' does not exist, skipping purge." fi fi # Create the bucket if it does not exist if ! checkBucketExists $BUCKET ; then echo "Creating bucket '$BUCKET'" ${MC} mb myminio/$BUCKET else echo "Bucket '$BUCKET' already exists." fi # set versioning for bucket if [ ! -z $VERSIONING ] ; then if [ $VERSIONING = true ] ; then echo "Enabling versioning for '$BUCKET'" ${MC} version enable myminio/$BUCKET...

# don't exit if this fails ${MC} rm -r --force myminio/$BUCKET set -e ; # reset `e` as active else echo "Bucket '$BUCKET' does not exist, skipping purge." fi fi # Create the bucket if it does not exist if ! checkBucketExists $BUCKET ; then echo "Creating bucket '$BUCKET'" ${MC} mb myminio/$BUCKET else echo "Bucket '$BUCKET' already exists." fi # set versioning for bucket if [ ! -z $VERSIONING ] ; then if [ $VERSIONING = true ] ; then echo "Enabling versioning for '$BUCKET'" ${MC} version enable myminio/$BUCKET...

# don't exit if this fails ${MC} rm -r --force myminio/$BUCKET set -e ; # reset `e` as active else echo "Bucket '$BUCKET' does not exist, skipping purge." fi fi # Create the bucket if it does not exist if ! checkBucketExists $BUCKET ; then echo "Creating bucket '$BUCKET'" ${MC} mb myminio/$BUCKET else echo "Bucket '$BUCKET' already exists." fi # set versioning for bucket if [ ! -z $VERSIONING ] ; then if [ $VERSIONING = true ] ; then echo "Enabling versioning for '$BUCKET'" ${MC} version enable myminio/$BUCKET...

# don't exit if this fails ${MC} rm -r --force myminio/$BUCKET set -e ; # reset `e` as active else echo "Bucket '$BUCKET' does not exist, skipping purge." fi fi # Create the bucket if it does not exist if ! checkBucketExists $BUCKET ; then echo "Creating bucket '$BUCKET'" ${MC} mb myminio/$BUCKET else echo "Bucket '$BUCKET' already exists." fi # set versioning for bucket if [ ! -z $VERSIONING ] ; then if [ $VERSIONING = true ] ; then echo "Enabling versioning for '$BUCKET'" ${MC} version enable myminio/$BUCKET...

   * Builder} constructor.
   */
  public static <E> Builder<E> builder() {
    return new Builder<>();
  }

  /**
   * A builder for creating immutable multiset instances, especially {@code public static final}
   * multisets ("constant multisets"). Example:
   *
   * {@snippet :
   * public static final ImmutableMultiset<Bean> BEANS =

    0x1.8ce85fadb707ep829,
    0x1.95d5f3d928edep945
  };

  /**
   * Returns {@code true} if {@code a} and {@code b} are within {@code tolerance} of each other.
   *
   * <p>Technically speaking, this is equivalent to {@code Math.abs(a - b) <= tolerance ||
   * Double.valueOf(a).equals(Double.valueOf(b))}.
   *
   * <p>Notable special cases include:
   *
   * <ul>
   *   <li>All NaNs are fuzzily equal.

/**
 * An object that can traverse the nodes that are reachable from a specified (set of) start node(s)
 * using a specified {@link SuccessorsFunction}.
 *
 * <p>There are two entry points for creating a {@code Traverser}: {@link
 * #forTree(SuccessorsFunction)} and {@link #forGraph(SuccessorsFunction)}. You should choose one
 * based on your answers to the following questions:
 *
 * <ol>

Alternatively, if you don't have a way to provide a command line option like `--root-path` or equivalent, you can set the `root_path` parameter when creating your FastAPI app:

{* ../../docs_src/behind_a_proxy/tutorial002_py310.py hl[3] *}

Passing the `root_path` to `FastAPI` would be the equivalent of passing the `--root-path` command line option to Uvicorn or Hypercorn.