////

### 在 Python 中读取环境变量

您还可以在 Python 之外的地方（例如终端中或使用任何其他方法）创建环境变量，然后在 Python 中读取它们。

例如，您可以有一个名为 `main.py` 的文件，其中包含以下内容：

```Python hl_lines="3"
import os

name = os.getenv("MY_NAME", "World")
print(f"Hello {name} from Python")
```

/// tip

<a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> 的第二个参数是要返回的默认值。

tristan da cunha","saint kitts and nevis","saint lucia","saint martin","saint pierre and miquelon","saint vincent and the grenadines","samoa","san marino","sao tome and principe","saudi arabia","senegal","serbia","seychelles","sierra leone","singapore","sint maarten","slovakia","slovenia","solomon islands","somalia","south africa","south georgia and the south sandwich islands","south sudan","spain","sri lanka","sudan","suriname","svalbard and jan mayen","swaziland","sweden","switzerland","syria","taiw...

👆 💪 💭 ⚫️ *➡ 🛠️ 🔢* 🍵 "👨‍🎨" (🍵 `@app.get("/some-path")`).

& ⚫️ 💪 📨 🕳 👆 💚.

👉 💼, 👉 🔗 ⌛:

* 📦 🔢 🔢 `q` 👈 `str`.
* 📦 🔢 🔢 `skip` 👈 `int`, & 🔢 `0`.
* 📦 🔢 🔢 `limit` 👈 `int`, & 🔢 `100`.

& ⤴️ ⚫️ 📨 `dict` ⚗ 📚 💲.

### 🗄 `Depends`

//// tab | 🐍 3️⃣.6️⃣ & 🔛

```Python hl_lines="3"
{!> ../../docs_src/dependencies/tutorial001.py!}
```

  }

  /**
   * This decodes a value into its contents using a preceding member of the same SEQUENCE. For
   * example, extensions type IDs specify what types to use for the corresponding values.
   *
   * If the hint is unknown [chooser] should return null which will cause the value to be decoded as
   * an opaque byte string.
   *
   * This may optionally wrap the contents in a tag.
   */

   * Content-Type header.
   */
  override fun toString(): String = commonToString()

  override fun equals(other: Any?): Boolean = commonEquals(other)

  override fun hashCode(): Int = commonHashCode()

  companion object {
    /**
     * Returns a media type for this string.
     *
     * @throws IllegalArgumentException if this is not a well-formed media type.
     */
    @JvmStatic

  void setValueReference(ValueReference<K, V> valueReference);

  /** Returns the next entry in the chain. */
  @CheckForNull
  ReferenceEntry<K, V> getNext();

  /** Returns the entry's hash. */
  int getHash();

  /** Returns the key for this entry. */
  @CheckForNull
  K getKey();

  /*
   * Used by entries that use access order. Access entries are maintained in a doubly-linked list.

  }

  public void testKeysElementSet() {
    assertEquals(multimap().keySet(), multimap().keys().elementSet());
  }

  @MapFeature.Require(SUPPORTS_REMOVE)
  public void testKeysRemove() {
    int original = multimap().keys().remove(k0(), 1);
    assertEquals(max(original - 1, 0), multimap().get(k0()).size());
  }

  @CollectionSize.Require(ONE)
  @CollectionFeature.Require(SUPPORTS_ITERATOR_REMOVE)

      return backingSortedSet;
    }

    @Override
    public boolean equals(@Nullable Object object) {
      return standardEquals(object);
    }

    @Override
    public int hashCode() {
      return standardHashCode();
    }

    @Override
    public boolean addAll(Collection<? extends T> collection) {
      return standardAddAll(collection);
    }

    @Override

      }

      @Override
      public List<String> order(List<String> insertionOrder) {
        List<String> order = Lists.newArrayList();
        for (String s : insertionOrder) {
          int index = order.indexOf(s);
          if (index == -1) {
            order.add(s);
          } else {
            order.add(index, s);
          }
        }
        return order;
      }
    };
  }

                stateMap.put(v, DfsState.VISITED);
            } else if (state == DfsState.VISITING) {
                // we are already visiting this vertex, this mean we have a cycle
                int pos = cycle.lastIndexOf(v.label);
                List<String> ret = cycle.subList(pos, cycle.size());
                ret.add(v.label);
                return ret;
            }
        }
        return null;