Throw an error when running integration installs when uv == False but pip is not installed

src/zenml/cli/integration.py

@@ -251,14 +251,19 @@ def install(
         force: Force the installation of the required packages.
         uv: Use uv for package installation (experimental).
     """
-    from zenml.cli.utils import is_uv_installed
+    from zenml.cli.utils import is_pip_installed, is_uv_installed
     from zenml.integrations.registry import integration_registry
 
     if uv and not is_uv_installed():
         error(
             "UV is not installed but the uv flag was passed in. Please install uv or remove the uv flag."
         )
 
+    if not uv and not is_pip_installed():
+        error(
+            "Pip is not installed. Please install pip or use the uv flag (--uv) for package installation."
+        )
+
     if not integrations:
         # no integrations specified, use all registered integrations
         integrations = set(integration_registry.integrations.keys())
@@ -346,12 +351,17 @@ def uninstall(
         force: Force the uninstallation of the required packages.
         uv: Use uv for package uninstallation (experimental).
     """
-    from zenml.cli.utils import is_uv_installed
+    from zenml.cli.utils import is_pip_installed, is_uv_installed
     from zenml.integrations.registry import integration_registry
 
     if uv and not is_uv_installed():
         error("Package `uv` is not installed. Please install it and retry.")
 
+    if not uv and not is_pip_installed():
+        error(
+            "Pip is not installed. Please install pip or use the uv flag (--uv) for package installation."
+        )
+
     if not integrations:
         # no integrations specified, use all registered integrations
         integrations = tuple(integration_registry.integrations.keys())
@@ -423,12 +433,17 @@ def upgrade(
         force: Force the installation of the required packages.
         uv: Use uv for package installation (experimental).
     """
-    from zenml.cli.utils import is_uv_installed
+    from zenml.cli.utils import is_pip_installed, is_uv_installed
     from zenml.integrations.registry import integration_registry
 
     if uv and not is_uv_installed():
         error("Package `uv` is not installed. Please install it and retry.")
 
+    if not uv and not is_pip_installed():
+        error(
+            "Pip is not installed. Please install pip or use the uv flag (--uv) for package installation."
+        )
+
     if not integrations:
         # no integrations specified, use all registered integrations
         integrations = set(integration_registry.integrations.keys())

src/zenml/cli/utils.py

@@ -1169,6 +1169,19 @@ def is_uv_installed() -> bool:
         return False
 
 
+def is_pip_installed() -> bool:
+    """Check if pip is installed in the current environment.
+
+    Returns:
+        True if pip is installed, False otherwise.
+    """
+    try:
+        pkg_resources.get_distribution("pip")
+        return True
+    except pkg_resources.DistributionNotFound:
+        return False
+
+
 def pretty_print_secret(
     secret: Dict[str, str],
     hide_secret: bool = True,