/// info

To use `EmailStr`, first install <a href="https://github.com/JoshData/python-email-validator" class="external-link" target="_blank">`email-validator`</a>.

Make sure you create a [virtual environment](../virtual-environments.md){.internal-link target=_blank}, activate it, and then install it, for example:

```console
$ pip install email-validator
```

or with:

```console

// Cap returns the capacity of the cache
func (c *LRU[K, V]) Cap() int {
	return c.size
}

// Entry is an LRU Entry
type Entry[K comparable, V any] struct {
	// Next and previous pointers in the doubly-linked list of elements.
	// To simplify the implementation, internally a list l is implemented
	// as a ring, such that &l.root is both the next element of the last
	// list element (l.Back()) and the previous element of the first list

 * @author shinsuke
 */
public class IllegalBlockSizeRuntimeException extends ClRuntimeException {

    private static final long serialVersionUID = 1L;

    /**
     * Creates a new {@link IllegalBlockSizeRuntimeException} with the specified cause.
     *
     * @param cause
     *            the cause
     */
    public IllegalBlockSizeRuntimeException(final IllegalBlockSizeException cause) {

 * the License.
 */

package com.google.common.base;

import com.google.common.annotations.GwtCompatible;

/**
 * The subset of the {@link java.util.regex.Matcher} API which is used by this package, and also
 * shared with the {@code re2j} library. For internal use only. Please refer to the {@code Matcher}
 * javadoc for details.
 */
@GwtCompatible

import org.jspecify.annotations.Nullable;

/**
 * Weak reference with a {@code finalizeReferent()} method which a background thread invokes after
 * the garbage collector reclaims the referent. This is a simpler alternative to using a {@link
 * ReferenceQueue}.
 *
 * @author Bob Lee
 * @since 2.0
 */
@J2ktIncompatible
@GwtIncompatible
public abstract class FinalizableWeakReference<T> extends WeakReference<T>
    implements FinalizableReference {

    validations:
      required: false
  - type: input
    id: page
    attributes:
      label: Page with the problem
      description: Please, provide a link to the relevant documentation page
    validations:

   * but the latest value for each key. This class exists only so that we can use {@link
   * MultimapsCollectionTest#populateMultimapForGet(Multimap, String[])} and similar methods to
   * populate a map to be passed to {@link Multimaps#forMap(Map)}. All tests should run against the
   * result of {@link #build()}.
   */
  private static final class PopulatableMapAsMultimap<K, V> extends ForwardingMultimap<K, V> {

```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> の第2引数は、デフォルトで返される値を指定します。

この引数を省略するとデフォルト値として`None`が返されますが、ここではデフォルト値として`"World"`を指定しています。

///

次に、このPythonプログラムを呼び出します。

//// tab | Linux, macOS, Windows Bash

    for (Object e : elements) {
      array[i++] = (String) e;
    }
    return create(array);
  }

  /**
   * Creates a new collection containing the given elements; implement this method instead of {@link
   * #create(Object...)}.
   */
  protected abstract List<String> create(String[] elements);

  @Override
  public String[] createArray(int length) {
    return new String[length];
  }

import com.google.common.collect.testing.features.CollectionSize;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code isEmpty()} operations on a map. Can't be invoked
 * directly; please see {@link com.google.common.collect.testing.MapTestSuiteBuilder}.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")