How to install lxml into virtualenv from the local system? - python

There is lxml module installed on my system (debian package python-lxml, for python 2.6), also I'm using virtualenv based on python2.6, installed with flag --no-site-packages.
Is it possible to install lxml inside virtual environment without compilation using some standard tools (pip, easy_install etc) and already install lxml binary files from the base system?
P.S.
I can, of course, manually create symlinks/copy files but don't like this method.

You may create required symlinks automatically by bootstrap script.

Related

building a package from source whose binary is already installed

I need to build a python module from source. It is just my second build and I'm a bit confused regarding the interaction between built packages and binaries installed through package manager.
Do I need to uninstall the binary first?
If I don't need to Will it overwrite the installed version or will both be available?
If it will not overwrite how can I import the built version into python?
Thank you all!
p.s: If it is case sensitive I'm on fedora 24 and the package is matplotlib which is installed through a setup.py.
I strongly recommend to use virtualenv and build your package inside. Is it really necessary to install via setup.py? If not, you can consider using pip to install your package inside virtualenv.

Why is my shared library given the suffix ".cpython-33m.so"?

I have a pip package that comes with a C library. The python module can't find the shared library. I noticed that it was given the name
librebound.cpython-33m.so
after the installation on CentOS, whereas on all other platforms it is just called librebound.so. Why is it getting the suffix cpython-33m.so and how can I prevent it?
I'm installing this in a virtual environment. Various version are:
Python 3.3.5
Virtualenv 13.0.3
pip 7.0.3

Modify PYTHONPATH to install packages into new "site-packages" path

I am working on an EC2 VM running Linux (I'm fairly new to Linux and Bash) which comes installed with Python 2.6. I upgraded to Python 2.7. When I try to install new modules, they install in /usr/lib/python2.6/site-packages but I need to change this to install in /usr/lib/python2.7/site-packages. I've tried a bunch of different ways to update the PYTHONPATH which I've found in various other post on Stackoverflow and other sites, but to no avail. Some I've tried are:
PYTHONPATH=$PYTHONPATH:/usr/lib/python2.7/site-packages export PYTHONPATH
PYTHONPATH="/usr/lib/python2.7/site-packages:$PYTHONPATH"
How can I update the install path to the new 2.7 path?
You covered how Python 2.7 was installed (which is a manual installation), how are you installing your modules?
If you sudo yum install <python-package>, you are going about this using system level (distribution specific) way of getting packages installed, which means it will only put packages in the system python location, in your case in the site-package directory in python2.6.
If you had used sudo pip install <python-package>, it should possibly work since you completely destroyed the default python installation which yum might have need (refer to Upgrade python without breaking yum).
With virtualenv, you can specify isolated, local locations for which you can install python packages to, isolating them from system level and you can fix a virtualenv to any available versions of python on your system, guaranteeing the right sets of libraries with the right sets of packages with all the correct versions (for python and the packages) specific to the needs of a particular application, which means you don't have to deal with the system/distribution level python path issues as that can be a huge source of headache. For example, on the system level you have a package by your distro that depends on some old versions of sqlalchemy, but in your actual application you need the most recent version, with virtualenv you can mask out the system level package and have the latest version installed locally there.

Where did python3.4 download to on my mac?

I decided today I better download python 3.4. So I go to the python/downloads page and do that. Now I am trying to make a new virtualenv using my new python module, mkvirtualenv -p python3.4 sandbox, but I get an error that it can't find my python executable.
The executable /Users/croberts/python3.4 (from --python=/Users/croberts/python3.4) does not exist
This is understandable, but I can't figure out where it is. The old versions of python are in /usr/bin/ but the new one didn't get installed there. How do you search for where a program is using the terminal?
According to the ReadMe.txt bundled with the installer, Python installs default to /Library/frameworks/Python.framework. I just did a test install and it ended up here specifically:
/Library/frameworks/Python.framework/versions/3.4/Python
Unless you changed the settings on the installer, that's where it should live. (If you installed it from source, I'd assume you'd know where you put it.) Something to note is that if you use Homebrew (and possibly other OSX package managers like MacPorts, though I haven't used it), installing Python through the PPC installer will cause a warning:
Warning: Python is installed at /Library/Frameworks/Python.framework
Homebrew only supports building against the System-provided Python or a
brewed Python. In particular, Pythons installed to /Library can interfere
with other software installs.
So if you do use Homebrew (and it's great), it's best to simply use brew install python3, which will put it into /usr/local/bin. Then you can alias python (or python3) to that version, instead.

What's the proper way to update Python packages when updating Python from 2.6 to 2.7?

I've installed A LOT of python packages for Python 2.6. Now I would like to upgrade Python to 2.7. Is there a proper or systematic way to update all the installed packages?
In my system, all the packages are installed at
/usr/lib64/python2.6/site-packages/ and
/usr/lib/python2.6/site-packages/
One obvious way is to install Python 2.7, download all the package sources or egg files, and re-install them one by one. However, Some useful packages like numpy and scipy are notorious for installation, especially when one needs to install from source. I expect I'll need to spend several hours to find the packages and solve the installation problems here and there.
Anyone has any suggestions on systematically update the installed packages?
First, you should not never ever ever ever install Python packages in in system library folder with easy_install using sudo on any operating system.
http://jamiecurle.co.uk/blog/installing-pip-virtualenv-and-virtualenvwrapper-on-os-x/#comment-573429347
The correct procedure would be make your installation procedure repeatable. There exist two commonly used solutions in Python world. These solutions automatically download correct versions of Python packages from http://pypi.python.org
PIP
pip and requirements.txt http://www.pip-installer.org/en/latest/requirements.html within virtualenv http://pypi.python.org/pypi/virtualenv
Buidout
Buildout, example from Plone CMS https://github.com/plone/Installers-UnifiedInstaller/blob/master/base_skeleton/versions.cfg
Buildout can also do configure, make, make install style installations for packages which need native libraries. For example there exist solution for libxml2 + lxml
http://pypi.python.org/pypi/z3c.recipe.staticlxml/
(Note: buildout does not need virtualenv as it does its own isolation from system Python)

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