Current File : //opt/alt/python37/share/doc/alt-python37-psycopg2-2.8.4/doc/src/install.rst
.. _installation:
Installation
============
.. sectionauthor:: Daniele Varrazzo <daniele.varrazzo@gmail.com>
Psycopg is a PostgreSQL_ adapter for the Python_ programming language. It is a
wrapper for the libpq_, the official PostgreSQL client library.
The `psycopg2` package is the current mature implementation of the adapter: it
is a C extension and as such it is only compatible with CPython_. If you want
to use Psycopg on a different Python implementation (PyPy, Jython, IronPython)
there is an experimental `porting of Psycopg for Ctypes`__, but it is not as
mature as the C implementation yet.
.. _PostgreSQL: https://www.postgresql.org/
.. _Python: https://www.python.org/
.. _libpq: https://www.postgresql.org/docs/current/static/libpq.html
.. _CPython: https://en.wikipedia.org/wiki/CPython
.. _Ctypes: https://docs.python.org/library/ctypes.html
.. __: https://github.com/mvantellingen/psycopg2-ctypes
.. index::
single: Prerequisites
Prerequisites
-------------
The current `!psycopg2` implementation supports:
..
NOTE: keep consistent with setup.py and the /features/ page.
- Python version 2.7
- Python 3 versions from 3.4 to 3.8
- PostgreSQL server versions from 7.4 to 12
- PostgreSQL client library version from 9.1
.. _build-prerequisites:
Build prerequisites
^^^^^^^^^^^^^^^^^^^
The build prerequisites are to be met in order to install Psycopg from source
code, from a source distribution package, GitHub_ or from PyPI.
.. _GitHub: https://github.com/psycopg/psycopg2
Psycopg is a C wrapper around the libpq_ PostgreSQL client library. To install
it from sources you will need:
- A C compiler.
- The Python header files. They are usually installed in a package such as
**python-dev**. A message such as *error: Python.h: No such file or
directory* is an indication that the Python headers are missing.
- The libpq header files. They are usually installed in a package such as
**libpq-dev**. If you get an *error: libpq-fe.h: No such file or directory*
you are missing them.
- The :program:`pg_config` program: it is usually installed by the
**libpq-dev** package but sometimes it is not in a :envvar:`PATH` directory.
Having it in the :envvar:`PATH` greatly streamlines the installation, so try
running ``pg_config --version``: if it returns an error or an unexpected
version number then locate the directory containing the :program:`pg_config`
shipped with the right libpq version (usually
``/usr/lib/postgresql/X.Y/bin/``) and add it to the :envvar:`PATH`:
.. code-block:: console
$ export PATH=/usr/lib/postgresql/X.Y/bin/:$PATH
You only need :program:`pg_config` to compile `!psycopg2`, not for its
regular usage.
Once everything is in place it's just a matter of running the standard:
.. code-block:: console
$ pip install psycopg2
or, from the directory containing the source code:
.. code-block:: console
$ python setup.py build
$ python setup.py install
Runtime requirements
^^^^^^^^^^^^^^^^^^^^
Unless you compile `!psycopg2` as a static library, or you install it from a
self-contained wheel package, it will need the libpq_ library at runtime
(usually distributed in a ``libpq.so`` or ``libpq.dll`` file). `!psycopg2`
relies on the host OS to find the library if the library is installed in a
standard location there is usually no problem; if the library is in a
non-standard location you will have to tell somehow Psycopg how to find it,
which is OS-dependent (for instance setting a suitable
:envvar:`LD_LIBRARY_PATH` on Linux).
.. note::
The libpq header files used to compile `!psycopg2` should match the
version of the library linked at runtime. If you get errors about missing
or mismatching libraries when importing `!psycopg2` check (e.g. using
:program:`ldd`) if the module ``psycopg2/_psycopg.so`` is linked to the
right ``libpq.so``.
.. note::
Whatever version of libpq `!psycopg2` is compiled with, it will be
possible to connect to PostgreSQL servers of any supported version: just
install the most recent libpq version or the most practical, without
trying to match it to the version of the PostgreSQL server you will have
to connect to.
.. index::
single: Install; from PyPI
single: Install; wheel
single: Wheel
.. _binary-packages:
Binary install from PyPI
------------------------
`!psycopg2` is also `available on PyPI`__ in the form of wheel_ packages for
the most common platform (Linux, OSX, Windows): this should make you able to
install a binary version of the module, not requiring the above build or
runtime prerequisites.
.. note::
The ``psycopg2-binary`` package is meant for beginners to start playing
with Python and PostgreSQL without the need to meet the build
requirements.
If you are the maintainer of a publish package depending on `!psycopg2`
**you shouldn't use 'psycopg2-binary' as a module dependency**. For
production use you are advised to use the source distribution.
Make sure to use an up-to-date version of :program:`pip` (you can upgrade it
using something like ``pip install -U pip``), then you can run:
.. code-block:: console
$ pip install psycopg2-binary
.. __: PyPI-binary_
.. _PyPI-binary: https://pypi.org/project/psycopg2-binary/
.. _wheel: https://pythonwheels.com/
.. note::
The binary packages come with their own versions of a few C libraries,
among which ``libpq`` and ``libssl``, which will be used regardless of other
libraries available on the client: upgrading the system libraries will not
upgrade the libraries used by `!psycopg2`. Please build `!psycopg2` from
source if you want to maintain binary upgradeability.
.. warning::
The `!psycopg2` wheel package comes packaged, among the others, with its
own ``libssl`` binary. This may create conflicts with other extension
modules binding with ``libssl`` as well, for instance with the Python
`ssl` module: in some cases, under concurrency, the interaction between
the two libraries may result in a segfault. In case of doubts you are
advised to use a package built from source.
.. index::
single: Install; disable wheel
single: Wheel; disable
.. _disable-wheel:
Change in binary packages between Psycopg 2.7 and 2.8
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In version 2.7.x, :command:`pip install psycopg2` would have tried to install
automatically the binary package of Psycopg. Because of concurrency problems
binary packages have displayed, ``psycopg2-binary`` has become a separate
package, and from 2.8 it has become the only way to install the binary
package.
If you are using Psycopg 2.7 and you want to disable the use of wheel binary
packages, relying on the system libraries available on your client, you
can use the :command:`pip` |--no-binary option|__, e.g.:
.. code-block:: console
$ pip install --no-binary :all: psycopg2
.. |--no-binary option| replace:: ``--no-binary`` option
.. __: https://pip.pypa.io/en/stable/reference/pip_install/#install-no-binary
which can be specified in your :file:`requirements.txt` files too, e.g. use:
.. code-block:: none
psycopg2>=2.7,<2.8 --no-binary psycopg2
to use the last bugfix release of the `!psycopg2` 2.7 package, specifying to
always compile it from source. Of course in this case you will have to meet
the :ref:`build prerequisites <build-prerequisites>`.
.. index::
single: setup.py
single: setup.cfg
Non-standard builds
-------------------
If you have less standard requirements such as:
- creating a :ref:`debug build <debug-build>`,
- using :program:`pg_config` not in the :envvar:`PATH`,
- supporting ``mx.DateTime``,
then take a look at the ``setup.cfg`` file.
Some of the options available in ``setup.cfg`` are also available as command
line arguments of the ``build_ext`` sub-command. For instance you can specify
an alternate :program:`pg_config` location using:
.. code-block:: console
$ python setup.py build_ext --pg-config /path/to/pg_config build
Use ``python setup.py build_ext --help`` to get a list of the options
supported.
.. index::
single: debug
single: PSYCOPG_DEBUG
.. _debug-build:
Creating a debug build
^^^^^^^^^^^^^^^^^^^^^^
In case of problems, Psycopg can be configured to emit detailed debug
messages, which can be very useful for diagnostics and to report a bug. In
order to create a debug package:
- `Download`__ and unpack the Psycopg source package.
- Edit the ``setup.cfg`` file adding the ``PSYCOPG_DEBUG`` flag to the
``define`` option.
- :ref:`Compile and install <build-prerequisites>` the package.
- Set the :envvar:`PSYCOPG_DEBUG` environment variable:
.. code-block:: console
$ export PSYCOPG_DEBUG=1
- Run your program (making sure that the `!psycopg2` package imported is the
one you just compiled and not e.g. the system one): you will have a copious
stream of informations printed on stderr.
.. __: http://initd.org/psycopg/download/
.. index::
single: tests
.. _test-suite:
Running the test suite
----------------------
Once `!psycopg2` is installed you can run the test suite to verify it is
working correctly. From the source directory, you can run:
.. code-block:: console
$ python -c "import tests; tests.unittest.main(defaultTest='tests.test_suite')" --verbose
The tests run against a database called ``psycopg2_test`` on UNIX socket and
the standard port. You can configure a different database to run the test by
setting the environment variables:
- :envvar:`PSYCOPG2_TESTDB`
- :envvar:`PSYCOPG2_TESTDB_HOST`
- :envvar:`PSYCOPG2_TESTDB_PORT`
- :envvar:`PSYCOPG2_TESTDB_USER`
The database should already exist before running the tests.
.. _other-problems:
If you still have problems
--------------------------
Try the following. *In order:*
- Read again the :ref:`build-prerequisites`.
- Read the :ref:`FAQ <faq-compile>`.
- Google for `!psycopg2` *your error message*. Especially useful the week
after the release of a new OS X version.
- Write to the `Mailing List`_.
- If you think that you have discovered a bug, test failure or missing feature
please raise a ticket in the `bug tracker`_.
- Complain on your blog or on Twitter that `!psycopg2` is the worst package
ever and about the quality time you have wasted figuring out the correct
:envvar:`ARCHFLAGS`. Especially useful from the Starbucks near you.
.. _mailing list: https://www.postgresql.org/list/psycopg/
.. _bug tracker: https://github.com/psycopg/psycopg2/issues
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