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psycopg vs psycopg-binary¶

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 published 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.

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.

Change in binary packages between Psycopg 2.7 and 2.8¶

In version 2.7.x, 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 pip --no-binary option, e.g.:

$ pip install --no-binary :all: psycopg2

which can be specified in your requirements.txt files too, e.g. use:

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 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.

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 or python3-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 pg_config program: it is usually installed by the
  libpq-dev package but sometimes it is not in a PATH directory.
  Having it in the 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 pg_config
  shipped with the right libpq version (usually
  /usr/lib/postgresql/X.Y/bin/) and add it to the PATH:

  $ export PATH=/usr/lib/postgresql/X.Y/bin/:$PATH
  

  You only need pg_config to compile psycopg2, not for its
  regular usage.

Once everything is in place it’s just a matter of running the standard:

or, from the directory containing the source code:

$ 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 Psycopg how to find it,
which is OS-dependent (for instance setting a suitable
LD_LIBRARY_PATH on Linux).

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 (the .tar.gz
  package).

• Edit the setup.cfg file adding the PSYCOPG_DEBUG flag to the
  define option.

• Compile and install the package.

• Set the PSYCOPG_DEBUG environment variable:

• 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.

Non-standard Python Implementation¶

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 a couple of alternative:

• a Ctypes port, but it is not as mature as the C implementation yet
  and it is not as feature-complete;

• a CFFI port which is currently more used and reported more efficient on
  PyPy, but please be careful of its version numbers because they are not
  aligned to the official psycopg2 ones and some features may differ.