# Environment Variables { #environment-variables }

/// tip

If you already know what "environment variables" are and how to use them, feel free to skip this.

///

An environment variable (also known as "**env var**") is a variable that lives **outside** of the Python code, in the **operating system**, and could be read by your Python code (or by other programs as well).

    }

    /**
     * Returns the system environment variable value for the specified key.
     *
     * @param key the environment variable key
     * @return the environment variable value, or null if not found
     */
    public static String getEnv(String key) {
        return System.getenv(key);
    }

    /**
     * Returns the system environment variable value for the specified key, or the default value if not found.

You can use the same builtin types as generics (with square brackets and types inside):

* `list`
* `tuple`
* `set`
* `dict`

#### List { #list }

For example, let's define a variable to be a `list` of `str`.

Declare the variable, with the same colon (`:`) syntax.

As the type, put `list`.

As the list is a type that contains some internal types, you put them in square brackets:

            // Expected due to missing dependencies in test environment
            assertTrue(true);
            return;
        }
        // assertEquals(0, result.size()); // Commented out due to variable scope
    }

    @Test
    public void test_getBoostedDocumentList_withVirtualHost() {
        KeyMatch keyMatch = new KeyMatch();
        keyMatch.setId("km1");
        keyMatch.setTerm("java");

    checkState(
        !(runtimeType instanceof TypeVariable),
        "Cannot construct a TypeToken for a type variable.\n"
            + "You probably meant to call new TypeToken<%s>(getClass()) "
            + "that can resolve the type variable for you.\n"
            + "If you do need to create a TypeToken of a type variable, "
            + "please use TypeToken.of() instead.",
        runtimeType);
  }

  /**

</div>

////

That command will create or modify some [environment variables](environment-variables.md) that will be available for the next commands.

One of those variables is the `PATH` variable.

/// tip

You can learn more about the `PATH` environment variable in the [Environment Variables](environment-variables.md#path-environment-variable) section.

///

//
// The class currently only interacts with single-slice (i.e., non-partitioned)
// variables.
class CheckpointReader {
 public:
  CheckpointReader(const std::string& filename, TF_Status* status);

  bool HasTensor(const std::string& name) const;
  const std::string DebugString() const;

  // Returns a map from variable names to their shapes.  Slices of a partitioned
  // tensor are combined into a single entry.

</pre>

<p>
Each iteration has its own separate declared variable (or variables)
[<a href="#Go_1.22">Go 1.22</a>].
The variable used by the first iteration is declared by the init statement.
The variable used by each subsequent iteration is declared implicitly before
executing the post statement and initialized to the value of the previous
iteration's variable at that moment.
</p>

<pre>
var prints []func()

# Settings and Environment Variables { #settings-and-environment-variables }

In many cases your application could need some external settings or configurations, for example secret keys, database credentials, credentials for email services, etc.

Most of these settings are variable (can change), like database URLs. And many could be sensitive, like secrets.

For this reason it's common to provide them in environment variables that are read by the application.

/// tip

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."
    fi
else
    JAVACMD=java
    if ! command -v java >/dev/null 2>&1
    then
        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.

Please set the JAVA_HOME variable in your environment to match the
location of your Java installation."