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python-3.7.4-docs-html/_sources/library/ensurepip.rst.txt

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+:mod:`ensurepip` --- Bootstrapping the ``pip`` installer
+========================================================
+
+.. module:: ensurepip
+   :synopsis: Bootstrapping the "pip" installer into an existing Python
+              installation or virtual environment.
+
+.. versionadded:: 3.4
+
+--------------
+
+The :mod:`ensurepip` package provides support for bootstrapping the ``pip``
+installer into an existing Python installation or virtual environment. This
+bootstrapping approach reflects the fact that ``pip`` is an independent
+project with its own release cycle, and the latest available stable version
+is bundled with maintenance and feature releases of the CPython reference
+interpreter.
+
+In most cases, end users of Python shouldn't need to invoke this module
+directly (as ``pip`` should be bootstrapped by default), but it may be
+needed if installing ``pip`` was skipped when installing Python (or
+when creating a virtual environment) or after explicitly uninstalling
+``pip``.
+
+.. note::
+
+   This module *does not* access the internet. All of the components
+   needed to bootstrap ``pip`` are included as internal parts of the
+   package.
+
+.. seealso::
+
+   :ref:`installing-index`
+      The end user guide for installing Python packages
+
+   :pep:`453`: Explicit bootstrapping of pip in Python installations
+      The original rationale and specification for this module.
+
+
+Command line interface
+----------------------
+
+The command line interface is invoked using the interpreter's ``-m`` switch.
+
+The simplest possible invocation is::
+
+    python -m ensurepip
+
+This invocation will install ``pip`` if it is not already installed,
+but otherwise does nothing. To ensure the installed version of ``pip``
+is at least as recent as the one bundled with ``ensurepip``, pass the
+``--upgrade`` option::
+
+    python -m ensurepip --upgrade
+
+By default, ``pip`` is installed into the current virtual environment
+(if one is active) or into the system site packages (if there is no
+active virtual environment). The installation location can be controlled
+through two additional command line options:
+
+* ``--root <dir>``: Installs ``pip`` relative to the given root directory
+  rather than the root of the currently active virtual environment (if any)
+  or the default root for the current Python installation.
+* ``--user``: Installs ``pip`` into the user site packages directory rather
+  than globally for the current Python installation (this option is not
+  permitted inside an active virtual environment).
+
+By default, the scripts ``pipX`` and ``pipX.Y`` will be installed (where
+X.Y stands for the version of Python used to invoke ``ensurepip``). The
+scripts installed can be controlled through two additional command line
+options:
+
+* ``--altinstall``: if an alternate installation is requested, the ``pipX``
+  script will *not* be installed.
+
+* ``--default-pip``: if a "default pip" installation is requested, the
+   ``pip`` script will be installed in addition to the two regular scripts.
+
+Providing both of the script selection options will trigger an exception.
+
+
+Module API
+----------
+
+:mod:`ensurepip` exposes two functions for programmatic use:
+
+.. function:: version()
+
+   Returns a string specifying the bundled version of pip that will be
+   installed when bootstrapping an environment.
+
+.. function:: bootstrap(root=None, upgrade=False, user=False, \
+                        altinstall=False, default_pip=False, \
+                        verbosity=0)
+
+   Bootstraps ``pip`` into the current or designated environment.
+
+   *root* specifies an alternative root directory to install relative to.
+   If *root* is ``None``, then installation uses the default install location
+   for the current environment.
+
+   *upgrade* indicates whether or not to upgrade an existing installation
+   of an earlier version of ``pip`` to the bundled version.
+
+   *user* indicates whether to use the user scheme rather than installing
+   globally.
+
+   By default, the scripts ``pipX`` and ``pipX.Y`` will be installed (where
+   X.Y stands for the current version of Python).
+
+   If *altinstall* is set, then ``pipX`` will *not* be installed.
+
+   If *default_pip* is set, then ``pip`` will be installed in addition to
+   the two regular scripts.
+
+   Setting both *altinstall* and *default_pip* will trigger
+   :exc:`ValueError`.
+
+   *verbosity* controls the level of output to :data:`sys.stdout` from the
+   bootstrapping operation.
+
+   .. note::
+
+      The bootstrapping process has side effects on both ``sys.path`` and
+      ``os.environ``. Invoking the command line interface in a subprocess
+      instead allows these side effects to be avoided.
+
+   .. note::
+
+      The bootstrapping process may install additional modules required by
+      ``pip``, but other software should not assume those dependencies will
+      always be present by default (as the dependencies may be removed in a
+      future version of ``pip``).