# Những bước đầu tiên

Tệp tin FastAPI đơn giản nhất có thể trông như này:

```Python
{!../../docs_src/first_steps/tutorial001.py!}
```

Sao chép sang một tệp tin `main.py`.

Chạy live server:

<div class="termy">

```console
$ uvicorn main:app --reload

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)

Now, let's see the module at `app/main.py`.

Here's where you import and use the class `FastAPI`.

This will be the main file in your application that ties everything together.

And as most of your logic will now live in its own specific module, the main file will be quite simple.

### Import `FastAPI`

You import and create a `FastAPI` class as normally.

     * cancelled.
     */
    @CheckForNull Executor delegate;

    /**
     * Set before calling delegate.execute(); set to null once run, so that it can be GCed; this
     * object may live on after, if submitAsync returns an incomplete future.
     */
    @CheckForNull Runnable task;

    /** Thread that called execute(). Set in execute, cleared when delegate.execute() returns. */

    long sum = 0L;
    for (AtomicLong value : map.values()) {
      sum = sum + value.get();
    }
    return sum;
  }

  @LazyInit @CheckForNull private transient Map<K, Long> asMap;

  /** Returns a live, read-only view of the map backing this {@code AtomicLongMap}. */
  public Map<K, Long> asMap() {
    Map<K, Long> result = asMap;
    return (result == null) ? asMap = createAsMap() : result;
  }

     * @return random source to use
     */
    SecureRandom getRandom ();


    /**
     * 
     * 
     * Property <tt>jcifs.smb.client.dfs.ttl</tt> (int, default 300)
     * 
     * @return title to live, in seconds, for DFS cache entries
     */
    long getDfsTtl ();


    /**
     * 
     * Property <tt>jcifs.smb.client.dfs.strictView</tt> (boolean, default false)
     * 

(It's not a subtraction, just idiosyncratic syntax.)
The frame size <code>$24-8</code> states that the function has a 24-byte frame
and is called with 8 bytes of argument, which live on the caller's frame.
If <code>NOSPLIT</code> is not specified for the <code>TEXT</code>,
the argument size must be provided.
For assembly functions with Go prototypes, <code>go</code> <code>vet</code> will check that the

    of the contribution must be compared against the cost of maintaining the
    feature.
*   Full new features (e.g., a new op implementing a cutting-edge algorithm)
    typically will live in
    [tensorflow/addons](https://github.com/tensorflow/addons) to get some
    airtime before a decision is made regarding whether they are to be migrated
    to the core.

// Cancellation/timeouts are removed, so parent cancellations/timeout will
// not propagate from parent.
// Context values are preserved.
// This can be used for goroutines that live beyond the parent context.
func bgContext(parent context.Context) context.Context {
	return bgCtx{parent: parent}
}

type bgCtx struct {
	parent context.Context
}

     * cancelled.
     */
    @CheckForNull Executor delegate;

    /**
     * Set before calling delegate.execute(); set to null once run, so that it can be GCed; this
     * object may live on after, if submitAsync returns an incomplete future.
     */
    @CheckForNull Runnable task;

    /** Thread that called execute(). Set in execute, cleared when delegate.execute() returns. */

    void setValue(S segment, E entry, V value);
  }

  /**
   * An entry in a hash table of a {@link Segment}.
   *
   * <p>Entries in the map can be in the following states:
   *
   * <p>Valid: - Live: valid key/value are set
   *
   * <p>Invalid: - Collected: key/value was partially collected, but not yet cleaned up
   */
  interface InternalEntry<K, V, E extends InternalEntry<K, V, E>> {