## Контекстные менеджеры { #context-managers }

### Что такое «контекстные менеджеры» { #what-are-context-managers }

«Контекстные менеджеры» — это любые объекты Python, которые можно использовать в операторе `with`.

例如，<a href="https://docs.python.org/zh-cn/3/tutorial/inputoutput.html#reading-and-writing-files" class="external-link" target="_blank">你可以使用`with`读取文件</a>：

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

在底层，`open("./somefile.txt")`创建了一个被称为"上下文管理器"的对象。

当 `with` 代码块结束时，它会确保关闭文件，即使发生了异常也是如此。

当你使用 `yield` 创建一个依赖项时，**FastAPI** 会在内部将其转换为上下文管理器，并与其他相关工具结合使用。

                context.parsingFailed,
                context.cwd,
                context.installationDirectory,
                context.userHomeDirectory,
                context.userProperties,
                context.systemProperties,
                context.topDirectory,
                context.rootDirectory,
                context.extensions,
                context.ciInfo,

        if (!result.errorPoms().isEmpty()) {
            context.failure("Strategy completed with errors");
            context.indent();
            context.info("Processed: " + result.processedPoms().size() + " POMs");
            context.info("Modified: " + result.modifiedPoms().size() + " POMs");
            context.failure("Errors: " + result.errorPoms().size() + " POMs");

        void testDefaultConstructor() {
            context = new PreauthIntegrityNegotiateContext();

            assertEquals(PreauthIntegrityNegotiateContext.NEGO_CTX_PREAUTH_TYPE, context.getContextType());
            assertNull(context.getHashAlgos());
            assertNull(context.getSalt());
        }

        @Test
        @DisplayName("Should handle null hash algorithms")

    protected void lookup(EncryptContext context) throws Exception {
        if (context.goals == null) {
            super.lookup(context);
            context.goals = context.lookup.lookupMap(Goal.class);
        }
    }

    @Override
    protected int execute(EncryptContext context) throws Exception {
        try {
            context.header = new ArrayList<>();
            context.style = new AttributedStyle();

    protected void lookup(UpgradeContext context) throws Exception {
        if (context.goals == null) {
            super.lookup(context);
            context.goals = context.lookup.lookupMap(Goal.class);
        }
    }

    @Override
    protected int execute(UpgradeContext context) throws Exception {
        try {
            context.header = new ArrayList<>();
            context.style = new AttributedStyle();

        assertActivation(false, newExistsProfile("someFile.txt"), context);
        assertActivation(false, newExistsProfile("${project.basedir}/someFile.txt"), context);

        assertActivation(false, newMissingProfile(null), context);
        assertActivation(true, newMissingProfile("someFile.txt"), context);
        assertActivation(true, newMissingProfile("${project.basedir}/someFile.txt"), context);
    }

     *
     * @param context the query context
     * @param termQuery the term query to convert
     * @param boost the boost value to apply
     * @return the converted QueryBuilder
     */
    protected QueryBuilder convertTermQuery(final QueryContext context, final TermQuery termQuery, final float boost) {
        final String field = getSearchField(context.getDefaultField(), termQuery.getTerm().field());

     * build a smaller set of projects but perform other operations in the context of your reactor.
     */
    private List<MavenProject> allProjects;

    private MavenProject topLevelProject;

    private ProjectDependencyGraph projectDependencyGraph;

    private boolean parallel;

    /**
     * Plugin context keyed by project ({@link MavenProject#getId()}) and by plugin lookup key