actions
@@ -104,7 +104,35 @@ steps:
 >The `setup-python` action does not handle authentication for pip when installing packages from private repositories. For help, refer [pip’s VCS support documentation](https://pip.pypa.io/en/stable/topics/vcs-support/) or visit the [pip repository](https://github.com/pypa/pip).
 
 See examples of using `cache` and `cache-dependency-path` for `pipenv` and `poetry` in the section: [Caching packages](docs/advanced-usage.md#caching-packages) of the [Advanced usage](docs/advanced-usage.md) guide.
+## Configuring a custom PyPI repository
 
+The action supports configuring pip to use a custom PyPI repository (e.g., a private Nexus, Artifactory, or other PyPI-compatible repository). This is useful in enterprise environments where the public PyPI may be blocked by a firewall, or where you need to use security-scanned packages from an internal repository.
+
+**Configure custom PyPI repository:**
+
+```yaml
+steps:
+- uses: actions/checkout@v5
+- uses: actions/setup-python@v6
+  with:
+    python-version: '3.13'
+    pypi-url: ${{ secrets.PYPI_REPO_URL }}
+    pypi-username: ${{ secrets.PYPI_USER }}
+    pypi-password: ${{ secrets.PYPI_PASSWORD }}
+- run: pip install -r requirements.txt
+```
+
+The action will create or overwrite a `pip.conf` (Linux/macOS) or `pip.ini` (Windows) file in the appropriate location with the configured repository URL and credentials. All subsequent pip commands will use the configured repository.
+
+> **Warning:** If a `pip.conf` or `pip.ini` file already exists at that location, its contents will be overwritten by this action for the duration of the job. Existing settings are not merged or preserved.
+**Input parameters:**
+- `pypi-url`: The URL of your custom PyPI repository (e.g., `https://nexus.example.com/repository/pypi/simple`)
+- `pypi-username` (optional): Username for authentication with the custom repository
+- `pypi-password` (optional): Password or token for authentication with the custom repository
+
+>**Note:** Both `pypi-username` and `pypi-password` must be provided together for authentication. If only one is provided, the action will configure pip without credentials.
+
+>**Security Note:** Always use GitHub secrets to store sensitive information like usernames and passwords. Never hardcode credentials in your workflow files.
 ## Advanced usage
 
 - [Using the python-version input](docs/advanced-usage.md#using-the-python-version-input)

@@ -17,7 +17,8 @@ import {
   isGhes,
   IS_WINDOWS,
   getDownloadFileName,
-  getVersionInputFromToolVersions
+  getVersionInputFromToolVersions,
+  configurePipRepository
 } from '../src/utils';
 
 jest.mock('@actions/cache');
@@ -378,3 +379,108 @@ describe('isGhes', () => {
     expect(isGhes()).toBeTruthy();
   });
 });
+
+describe('configurePipRepository', () => {
+  const originalHome = process.env.HOME;
+  const originalUserProfile = process.env.USERPROFILE;
+  const testHome = path.join(tempDir, 'home');
+
+  beforeEach(() => {
+    // Setup test home directory
+    process.env.HOME = testHome;
+    process.env.USERPROFILE = testHome;
+    if (fs.existsSync(testHome)) {
+      fs.rmSync(testHome, {recursive: true, force: true});
+    }
+    fs.mkdirSync(testHome, {recursive: true});
+  });
+
+  afterEach(() => {
+    // Cleanup
+    if (fs.existsSync(testHome)) {
+      fs.rmSync(testHome, {recursive: true, force: true});
+    }
+    process.env.HOME = originalHome;
+    process.env.USERPROFILE = originalUserProfile;
+  });
+
+  it('creates pip config file with URL only', async () => {
+    const pypiUrl = 'https://nexus.example.com/repository/pypi/simple';
+    await configurePipRepository(pypiUrl);
+
+    const configDir = IS_WINDOWS
+      ? path.join(testHome, 'pip')
+      : path.join(testHome, '.pip');
+    const configFile = IS_WINDOWS ? 'pip.ini' : 'pip.conf';
+    const configPath = path.join(configDir, configFile);
+
+    expect(fs.existsSync(configPath)).toBeTruthy();
+    const content = fs.readFileSync(configPath, 'utf8');
+    expect(content).toContain('[global]');
+    expect(content).toContain(`index-url = ${pypiUrl}`);
+  });
+
+  it('creates pip config file with credentials', async () => {
+    const pypiUrl = 'https://nexus.example.com/repository/pypi/simple';
+    const username = 'testuser';
+    const password = 'testpass';
+    await configurePipRepository(pypiUrl, username, password);
+
+    const configDir = IS_WINDOWS
+      ? path.join(testHome, 'pip')
+      : path.join(testHome, '.pip');
+    const configFile = IS_WINDOWS ? 'pip.ini' : 'pip.conf';
+    const configPath = path.join(configDir, configFile);
+
+    expect(fs.existsSync(configPath)).toBeTruthy();
+    const content = fs.readFileSync(configPath, 'utf8');
+    expect(content).toContain('[global]');
+    const encodedUsername = encodeURIComponent(username);
+    const encodedPassword = encodeURIComponent(password);
+    expect(content).toContain(`index-url = https://${encodedUsername}:${encodedPassword}@`);
+    expect(content).toContain('nexus.example.com/repository/pypi/simple');
+  });
+
+  it('does nothing when pypiUrl is not provided', async () => {
+    await configurePipRepository('');
+
+    const configDir = IS_WINDOWS
+      ? path.join(testHome, 'pip')
+      : path.join(testHome, '.pip');
+
+    expect(fs.existsSync(configDir)).toBeFalsy();
+  });
+
+  it('warns when only username is provided', async () => {
+    const warningMock = jest.spyOn(core, 'warning');
+    const pypiUrl = 'https://nexus.example.com/repository/pypi/simple';
+    const username = 'testuser';
+    await configurePipRepository(pypiUrl, username);
+
+    expect(warningMock).toHaveBeenCalledWith(
+      'Both pypi-username and pypi-password must be provided for authentication. Configuring without credentials.'
+    );
+  });
+
+  it('warns when only password is provided', async () => {
+    const warningMock = jest.spyOn(core, 'warning');
+    const pypiUrl = 'https://nexus.example.com/repository/pypi/simple';
+    const password = 'testpass';
+    await configurePipRepository(pypiUrl, undefined, password);
+
+    expect(warningMock).toHaveBeenCalledWith(
+      'Both pypi-username and pypi-password must be provided for authentication. Configuring without credentials.'
+    );
+  });
+
+  it('creates config directory if it does not exist', async () => {
+    const pypiUrl = 'https://nexus.example.com/repository/pypi/simple';
+    const configDir = IS_WINDOWS
+      ? path.join(testHome, 'pip')
+      : path.join(testHome, '.pip');
+
+    expect(fs.existsSync(configDir)).toBeFalsy();
+    await configurePipRepository(pypiUrl);
+    expect(fs.existsSync(configDir)).toBeTruthy();
+  });
+});
@@ -33,6 +33,15 @@ inputs:
     description: "Used to specify the version of pip to install with the Python. Supported format: major[.minor][.patch]."
   pip-install:
     description: "Used to specify the packages to install with pip after setting up Python. Can be a requirements file or package names."
+  pypi-url:
+    description: "Used to specify a custom PyPI repository URL. When set, pip will be configured to use this repository."
+    required: false
+  pypi-username:
+    description: "Username for authentication with the custom PyPI repository. Used with 'pypi-url'."
+    required: false
+  pypi-password:
+    description: "Password or token for authentication with the custom PyPI repository. Used with 'pypi-url'."
+    required: false
 outputs:
   python-version:
     description: "The installed Python or PyPy version. Useful when given a version range as input."

@@ -11,7 +11,8 @@ import {
   logWarning,
   IS_MAC,
   getVersionInputFromFile,
-  getVersionsInputFromPlainFile
+  getVersionsInputFromPlainFile,
+  configurePipRepository
 } from './utils';
 import {exec} from '@actions/exec';
 
@@ -159,6 +160,18 @@ async function run() {
       if (cache && isCacheFeatureAvailable()) {
         await cacheDependencies(cache, pythonVersion);
       }
+      const pypiUrl = core.getInput('pypi-url');
+      if (pypiUrl) {
+        const pypiUsername = core.getInput('pypi-username');
+        const pypiPassword = core.getInput('pypi-password');
+        if (pypiUsername && pypiUsername.trim()) {
+          core.setSecret(pypiUsername);
+        }
+        if (pypiPassword && pypiPassword.trim()) {
+          core.setSecret(pypiPassword);
+        }
+        await configurePipRepository(pypiUrl, pypiUsername, pypiPassword);
+      }
       const pipInstall = core.getInput('pip-install');
       if (pipInstall) {
         await installPipPackages(pipInstall);

@@ -422,3 +422,79 @@ export function getDownloadFileName(downloadUrl: string): string | undefined {
     ? path.join(tempDir, path.basename(downloadUrl))
     : undefined;
 }
+
+/**
+ * Configure pip to use a custom PyPI repository
+ * Creates a pip.conf (Linux/macOS) or pip.ini (Windows) file with repository and credentials
+ * @param pypiUrl The custom PyPI repository URL
+ * @param username The username for authentication (optional)
+ * @param password The password or token for authentication (optional)
+ */
+export async function configurePipRepository(
+  pypiUrl: string,
+  username?: string,
+  password?: string
+): Promise<void> {
+  if (!pypiUrl) {
+    return;
+  }
+
+  core.info(`Configuring pip to use custom PyPI repository: ${pypiUrl}`);
+
+  // Determine the pip config file location and name based on OS
+  const homeDir = process.env.HOME || process.env.USERPROFILE || '';
+  const configDir = IS_WINDOWS
+    ? path.join(homeDir, 'pip')
+    : path.join(homeDir, '.pip');
+  const configFile = IS_WINDOWS ? 'pip.ini' : 'pip.conf';
+  const configPath = path.join(configDir, configFile);
+
+  // Create the config directory if it doesn't exist
+  if (!fs.existsSync(configDir)) {
+    fs.mkdirSync(configDir, {recursive: true});
+  }
+
+  // Build the index URL with credentials if provided
+  let indexUrl = pypiUrl;
+  if (username && password) {
+    // Parse the URL to inject credentials
+    try {
+      const url = new URL(pypiUrl);
+      url.username = encodeURIComponent(username);
+      url.password = encodeURIComponent(password);
+      indexUrl = url.toString();
+    } catch (error) {
+      core.warning(
+        `Failed to parse PyPI URL: ${pypiUrl}. Using URL without credentials.`
+      );
+      indexUrl = pypiUrl;
+    }
+  } else if (username || password) {
+    core.warning(
+      'Both pypi-username and pypi-password must be provided for authentication. Configuring without credentials.'
+    );
+  }
+
+  // Create the pip config content
+  const configContent = `[global]
+index-url = ${indexUrl}
+`;
+
+  // Write the config file
+  try {
+    fs.writeFileSync(configPath, configContent, {encoding: 'utf8'});
+    core.info(`Successfully created pip config file at: ${configPath}`);
+
+    // Mask credentials in logs if they were used
+    if (username) {
+      core.setSecret(username);
+    }
+    if (password) {
+      core.setSecret(password);
+    }
+  } catch (error) {
+    core.setFailed(
+      `Failed to create pip config file at ${configPath}: ${error}`
-    core.setFailed(
-      `Failed to create pip config file at ${configPath}: ${error}`
+    const errorMessage =
+      error instanceof Error ? error.message : String(error);
+    core.setFailed(
+      `Failed to create pip config file at ${configPath}: ${errorMessage}`
-    core.setFailed(
-      `Failed to create pip config file at ${configPath}: ${error}`
+    const errorMessage =
+      error instanceof Error ? error.message : String(error);
+    core.setFailed(
+      `Failed to create pip config file at ${configPath}: ${errorMessage}`
+    );
-    );
+    );
+    throw error instanceof Error
+      ? error
+      : new Error(
+          `Failed to create pip config file at ${configPath}: ${error}`
+        );
-    );
+    );
+    throw error instanceof Error
+      ? error
+      : new Error(
+          `Failed to create pip config file at ${configPath}: ${error}`
+        );
+  }
+}