Khi bạn làm việc trong các dự án Python, bạn có thể sử dụng một **môi trường ảo** (hoặc một cơ chế tương tự) để cách ly các gói bạn cài đặt cho mỗi dự án.

/// info
Nếu bạn đã biết về các môi trường ảo, cách tạo chúng và sử dụng chúng, bạn có thể bỏ qua phần này. 🤓

///

/// tip

Một **môi trường ảo** khác với một **biến môi trường (environment variable)**.

Một **biến môi trường** là một biến trong hệ thống có thể được sử dụng bởi các chương trình.

     * the parameter and return type both to be platform types. As a result, Kotlin permits calls
     * that can lead to NullPointerException. That's unfortunate. But hopefully most Kotlin callers
     * use `get(key) ?: defaultValue` instead of this method, anyway.
     */
    V result = get(key);
    // TODO(b/192579700): Use a ternary once it no longer confuses our nullness checker.

time (GCE PDs attached in RW mode, for example), then the volume must be
manually detached before Kubernetes can attach it to other nodes.
  * If a volume is already attached to a node any subsequent attempts to attach it
again (due to kubelet restart, for example) will fail. The volume must either
be manually detached first or the pods referencing it deleted (which would
trigger automatic volume detach).

     * the parameter and return type both to be platform types. As a result, Kotlin permits calls
     * that can lead to NullPointerException. That's unfortunate. But hopefully most Kotlin callers
     * use `get(key) ?: defaultValue` instead of this method, anyway.
     */
    V result = get(key);
    // TODO(b/192579700): Use a ternary once it no longer confuses our nullness checker.

  /**
   * Returns a new hash set using the smallest initial table size that can hold {@code expectedSize}
   * elements without resizing. Note that this is not what {@link HashSet#HashSet(int)} does, but it
   * is what most users want and expect it to do.
   *
   * <p>This behavior can't be broadly guaranteed, but has been tested with OpenJDK 1.7 and 1.8.
   *
   * @param expectedSize the number of elements you expect to add to the returned set

          </description>
          <type>String</type>
        </field>
        <field>
          <name>post</name>
          <version>3.0.0+</version>
          <description>
            The email address or link that can be used to post to
            the mailing list.  If this is an email address, a
            {@code mailto:} link will automatically be created

	hasSessionPolicy, isAllowedSP := isAllowedBySessionPolicy(args)
	if hasSessionPolicy {
		return isAllowedSP && (isOwnerDerived || combinedPolicy.IsAllowed(args))
	}

	// Sub policy not set, this is most common since subPolicy
	// is optional, use the inherited policies.
	return isOwnerDerived || combinedPolicy.IsAllowed(args)
}

      cache.edit(key)
    }.also { expected ->
      assertThat(expected.message).isEqualTo("keys must match regex [a-z0-9_-]{1,120}: \"$key\"")
    }
    assertFailsWith<IllegalArgumentException> {
      key = "has_CR\r"
      cache.edit(key)
    }.also { expected ->
      assertThat(expected.message).isEqualTo("keys must match regex [a-z0-9_-]{1,120}: \"$key\"")
    }
    assertFailsWith<IllegalArgumentException> {

<div class="termy">

```console
$ cd ~/code/prisoner-of-azkaban

$ python main.py

// Error importing sirius, it's not installed 😱
Traceback (most recent call last):
    File "main.py", line 1, in <module>
        import sirius
```

</div>

    dummyValue = new Object();
    dummyValueRef = map.newValueReference(dummy, dummyValue, 1);
    dummy.setValueReference(dummyValueRef);
    table.set(index, dummy);
    // returns the most recent entry
    assertSame(dummyValue, segment.get(key, hash));
    assertTrue(segment.containsKey(key, hash));
    assertTrue(segment.containsValue(value));
    assertTrue(segment.containsValue(dummyValue));