Develop Reference

How do I install a Python library? [duplicate]

I'm having a hard time setting up python packages. EasyInstall from SetupTools is supposed to help that, but they don't have an executable for Python 2.6.
For instance to install Mechanize, I'm just supposed to put the Mechanize folder in C:\Python24\Lib\site-packages according to INSTALL.txt, but runnning the tests does not work. Can someone help shed some light on this? Thanks!

The accepted answer is outdated. So first, pip is preferred over easy_install, (Why use pip over easy_install?). Then follow these steps to install pip on Windows, it's quite easy.
Install setuptools:
curl https://bootstrap.pypa.io/ez_setup.py | python
Install pip:
curl https://bootstrap.pypa.io/get-pip.py | python
Optionally, you can add the path to your environment so that you can use pip anywhere. It's somewhere like C:\Python33\Scripts.

Newer versions of Python for Windows come with the pip package manager. (source)
pip is already installed if you're using Python 2 >=2.7.9 or Python 3 >=3.4
Use that to install packages:
cd C:\Python\Scripts\
pip.exe install <package-name>
So in your case it'd be:
pip.exe install mechanize

This is a good tutorial on how to get easy_install on windows. The short answer: add C:\Python26\Scripts (or whatever python you have installed) to your PATH.

You don't need the executable for setuptools.
You can download the source code, unpack it, traverse to the downloaded directory and run python setup.py install in the command prompt

Starting with Python 2.7, pip is included by default. Simply download your desired package via
python -m pip install [package-name]

As I wrote elsewhere
Packaging in Python is dire. The root cause is that the language ships without a package manager.
Fortunately, there is one package manager for Python, called Pip. Pip is inspired by Ruby's Gem, but lacks some features. Ironically, Pip itself is complicated to install. Installation on the popular 64-bit Windows demands building and installing two packages from source. This is a big ask for anyone new to programming.
So the right thing to do is to install pip. However if you can't be bothered, Christoph Gohlke provides binaries for popular Python packages for all Windows platforms http://www.lfd.uci.edu/~gohlke/pythonlibs/
In fact, building some Python packages requires a C compiler (eg. mingw32) and library headers for the dependencies. This can be a nightmare on Windows, so remember the name Christoph Gohlke.

I had problems in installing packages on Windows. Found the solution. It works in Windows7+. Mainly anything with Windows Powershell should be able to make it work. This can help you get started with it.
Firstly, you'll need to add python installation to your PATH variable. This should help.
You need to download the package in zip format that you are trying to install and unzip it. If it is some odd zip format use 7Zip and it should be extracted.
Navigate to the directory extracted with setup.py using Windows Powershell (Use link for it if you have problems)
Run the command python setup.py install
That worked for me when nothing else was making any sense. I use Python 2.7 but the documentation suggests that same would work for Python 3.x also.

Upgrade the pip via command prompt ( Python Directory )
D:\Python 3.7.2>python -m pip install --upgrade pip
Now you can install the required Module
D:\Python 3.7.2>python -m pip install <<yourModuleName>>

pip is the package installer for python, update it first, then download what you need
python -m pip install --upgrade pip
Then:
python -m pip install <package_name>

You can also just download and run ez_setup.py, though the SetupTools documentation no longer suggests this. Worked fine for me as recently as 2 weeks ago.

PS D:\simcut> C:\Python27\Scripts\pip.exe install networkx
Collecting networkx
c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\util\ssl_.py:318: SNIMissingWarning: An HTTPS reques
t has been made, but the SNI (Subject Name Indication) extension to TLS is not available on this platform. This may caus
e the server to present an incorrect TLS certificate, which can cause validation failures. You can upgrade to a newer ve
rsion of Python to solve this. For more information, see https://urllib3.readthedocs.io/en/latest/security.html#snimissi
ngwarning.
SNIMissingWarning
c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\util\ssl_.py:122: InsecurePlatformWarning: A true SS
LContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL con
nections to fail. You can upgrade to a newer version of Python to solve this. For more information, see https://urllib3.
readthedocs.io/en/latest/security.html#insecureplatformwarning.
InsecurePlatformWarning
Downloading networkx-1.11-py2.py3-none-any.whl (1.3MB)
100% |################################| 1.3MB 664kB/s
Collecting decorator>=3.4.0 (from networkx)
Downloading decorator-4.0.11-py2.py3-none-any.whl
Installing collected packages: decorator, networkx
Successfully installed decorator-4.0.11 networkx-1.11
c:\python27\lib\site-packages\pip\_vendor\requests\packages\urllib3\util\ssl_.py:122: InsecurePlatformWarning: A true SSLContext object i
s not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. You can upgrade
to a newer version of Python to solve this. For more information, see https://urllib3.readthedocs.io/en/latest/security.html#insecureplat
formwarning.
InsecurePlatformWarning
Or just put the directory to your pip executable in your system path.

As mentioned by Blauhirn after 2.7 pip is preinstalled. If it is not working for you it might need to be added to path.
However if you run Windows 10 you no longer have to open a terminal to install a module. The same goes for opening Python as well.
You can type directly into the search menu pip install mechanize, select command and it will install:
If anything goes wrong however it may close before you can read the error but still it's a useful shortcut.

Where does pip install its modules? What if using a virtualenv? Also getting an error setting up mod_wsgi

I am new to Python and there are some things which I am not able to apprehend. Questions may seem like very kiddish, so bear with me.
As you know, Ubuntu comes with an outdated Python version. I wished to use the latest python. But since it is recommended not to override the system's python, I installed virtualenv.
I installed pip first, using sudo apt-get install python-pip.
Then installed virtualenv, using sudo pip install virtualenv, and did all the configurations required to link it to the latest python.
The questions which I want to ask are-
Where does the command pip install <module> store the module in the system? I am asking this question because there is a section in this link, which says "Installation into Python". I was confused by this, thinking whether installing a python module is sensitive to which python version I am using. If it is so, then where does pip install the module if I am using virtualenv and otherwise.
I have manually installed Apache HTTP Server 2.4.23 using this link. While installing mod_wsgi using command sudo pip install mod_wsgi, I am getting this error
RuntimeError: The 'apxs' command appears not to be installed or is not
executable. Please check the list of prerequisites in the
documentation for this package and install any missing Apache httpd
server packages.
I searched for it and the solution is to install developer package of Apache. But the problem is that I am not able to find it anywhere on it's site. I want to install it manually. What to do? Also, If I install it through sudo apt-get install apache2-dev, Will there be any difference ?
Note: As mentioned on this link, I have already set the value of APXS environment variable to the location of apxs script, which is /usr/local/apache/bin/apxs.

Concerning 1., if I have well understood, you would like to have the last 2.7 or 3.5 Python version on your distribution. Actually, you can have multiple python distribution on your distribution. I would suggest you to have a look on conda/anaconda (https://www.continuum.io/downloads) : it is very powerful and i think it would better suit you than virtualenv: virtualenv would enable you to create a separate python environnement, but it would not install a newer version of Python.
Concerning 2, I am not an expert in Apache2, but I would have used apt-get instead of re-compiling apache. While compiling, you may need some dependancies to build the mod_wsgi module. So I think it is way more easy to use the pre-built packages from your ubuntu.

python bdist_rpm not using install_requires?

I've created a new RPM using python bdist_rpm . Normally python setup.py install would install python dependencies like websocket-client or any other package. But the RPM just refuses to install anything.
Apparently the suggestion from various other posts seem to be in the line of just requiring them in setup.cfg as rpm packages. This doesn't make sense to me since most of the rpm packages seem to be on really old version and I can't possibly create rpms for all the python packages i require. I need a much recent version and it doesn't make sense that the yum installs don't actually install the packages.
What is the right (clean and easiest) way to do it ? I believe if a setup.py has something like
install_requires=[
"validictory",
"requests",
"netlogger>=4.3.0",
"netifaces",
"pyzmq",
"psutil",
"docopt"
],
Then it should try to either include them in the rpm or try to install it.
I am trying on a clean centos vm using vagrant which I keep destroying and then install the rpm.

Well the super hack way i used was to just add a post install script with all the requirements as easy_install installation (instead of pip because older versions may not have pip and even after installing pip, the approach failed on systems with python 2.6)
#Adding this in setup.py
options = {'bdist_rpm':{'post_install' : 'scripts/rpm_postinstall.sh'}},
Then the script is as follows:
easy_install -U <pkgnames>
Of course a post_uninstall can also be added if you want to clean up which I wouldn't because you have no clue what is using the packages installed apart from this app.
The logic of the rpm approach seems to be for this but its honestly over engineering and I'd rather package all the modules with the rpm to ensure it always works. ** Screaming out for a cleaner solution **

Installing SOAP for Python

I am new to Python, trying to learn it by doing a tutorial based on "Dive into Python" book.
I am already in chapter about SOAP and I encountered some problems, when I tried to install all required libraries to use SOAP.
The tutorial says I need 3 libraries:
PyXML, fpconst, SOAPpy
I've installed fpconst succesfully.
However I can't install two others. I read on some forum that to install SOAPpy I need to have PyXML already installed, so maybe the problem is only in the first library.
I followed instructions in README, but I'm getting some error and I don't really know what is wrong and how can solve it. See screen for details. My version of Python is 2.7.2+ and I am trying to install PyXML version 0.8.4.
Full size
The errors states that such file or directory does not exist.
I am using Ubuntu 11.10.
PS: Ah! I forgot to mention that. I downloaded PyXML from this source :
http://sourceforge.net/projects/pyxml/
And it it written here that it is out of date and one shouldn't use it. So what is an alternative to PyXML?

If you are using Ubuntu, why not just install these with your package manager?
sudo apt-get install python-lxml python-fpconst python-soappy
The package manager should be your preferred way to install any software in a Linux distro - it will make your life a lot easier, and ensure you keep things up-to-date and can easily uninstall them.
Failing that, you could also use PyPi - the Python Package Index.
pip install lxml
pip install fpconst
pip install soappy

Why use pip over easy_install?

A tweet reads:
Don't use easy_install, unless you
like stabbing yourself in the face.
Use pip.
Why use pip over easy_install? Doesn't the fault lie with PyPI and package authors mostly? If an author uploads crap source tarball (eg: missing files, no setup.py) to PyPI, then both pip and easy_install will fail. Other than cosmetic differences, why do Python people (like in the above tweet) seem to strongly favor pip over easy_install?
(Let's assume that we're talking about easy_install from the Distribute package, that is maintained by the community)

From Ian Bicking's own introduction to pip:
pip was originally written to improve on easy_install in the following ways
All packages are downloaded before installation. Partially-completed installation doesn’t occur as a result.
Care is taken to present useful output on the console.
The reasons for actions are kept track of. For instance, if a package is being installed, pip keeps track of why that package was required.
Error messages should be useful.
The code is relatively concise and cohesive, making it easier to use programmatically.
Packages don’t have to be installed as egg archives, they can be installed flat (while keeping the egg metadata).
Native support for other version control systems (Git, Mercurial and Bazaar)
Uninstallation of packages.
Simple to define fixed sets of requirements and reliably reproduce a set of packages.

Many of the answers here are out of date for 2015 (although the initially accepted one from Daniel Roseman is not). Here's the current state of things:
Binary packages are now distributed as wheels (.whl files)—not just on PyPI, but in third-party repositories like Christoph Gohlke's Extension Packages for Windows. pip can handle wheels; easy_install cannot.
Virtual environments (which come built-in with 3.4, or can be added to 2.6+/3.1+ with virtualenv) have become a very important and prominent tool (and recommended in the official docs); they include pip out of the box, but don't even work properly with easy_install.
The distribute package that included easy_install is no longer maintained. Its improvements over setuptools got merged back into setuptools. Trying to install distribute will just install setuptools instead.
easy_install itself is only quasi-maintained.
All of the cases where pip used to be inferior to easy_install—installing from an unpacked source tree, from a DVCS repo, etc.—are long-gone; you can pip install ., pip install git+https://.
pip comes with the official Python 2.7 and 3.4+ packages from python.org, and a pip bootstrap is included by default if you build from source.
The various incomplete bits of documentation on installing, using, and building packages have been replaced by the Python Packaging User Guide. Python's own documentation on Installing Python Modules now defers to this user guide, and explicitly calls out pip as "the preferred installer program".
Other new features have been added to pip over the years that will never be in easy_install. For example, pip makes it easy to clone your site-packages by building a requirements file and then installing it with a single command on each side. Or to convert your requirements file to a local repo to use for in-house development. And so on.
The only good reason that I know of to use easy_install in 2015 is the special case of using Apple's pre-installed Python versions with OS X 10.5-10.8. Since 10.5, Apple has included easy_install, but as of 10.10 they still don't include pip. With 10.9+, you should still just use get-pip.py, but for 10.5-10.8, this has some problems, so it's easier to sudo easy_install pip. (In general, easy_install pip is a bad idea; it's only for OS X 10.5-10.8 that you want to do this.) Also, 10.5-10.8 include readline in a way that easy_install knows how to kludge around but pip doesn't, so you also want to sudo easy_install readline if you want to upgrade that.

Another—as of yet unmentioned—reason for favoring pip is because it is the new hotness and will continue to be used in the future.
The infographic below—from the Current State of Packaging section in the The Hitchhiker's Guide to Packaging v1.0—shows that setuptools/easy_install will go away in the future.
Here's another infographic from distribute's documentation showing that Setuptools and easy_install will be replaced by the new hotness—distribute and pip. While pip is still the new hotness, Distribute merged with Setuptools in 2013 with the release of Setuptools v0.7.

Two reasons, there may be more:
pip provides an uninstall command
if an installation fails in the middle, pip will leave you in a clean state.

REQUIREMENTS files.
Seriously, I use this in conjunction with virtualenv every day.
QUICK DEPENDENCY MANAGEMENT TUTORIAL, FOLKS
Requirements files allow you to create a snapshot of all packages that have been installed through pip. By encapsulating those packages in a virtualenvironment, you can have your codebase work off a very specific set of packages and share that codebase with others.
From Heroku's documentation https://devcenter.heroku.com/articles/python
You create a virtual environment, and set your shell to use it. (bash/*nix instructions)
virtualenv env
source env/bin/activate
Now all python scripts run with this shell will use this environment's packages and configuration. Now you can install a package locally to this environment without needing to install it globally on your machine.
pip install flask
Now you can dump the info about which packages are installed with
pip freeze > requirements.txt
If you checked that file into version control, when someone else gets your code, they can setup their own virtual environment and install all the dependencies with:
pip install -r requirements.txt
Any time you can automate tedium like this is awesome.

pip won't install binary packages and isn't well tested on Windows.
As Windows doesn't come with a compiler by default pip often can't be used there. easy_install can install binary packages for Windows.

UPDATE: setuptools has absorbed distribute as opposed to the other way around, as some thought. setuptools is up-to-date with the latest distutils changes and the wheel format. Hence, easy_install and pip are more or less on equal footing now.
Source: http://pythonhosted.org/setuptools/merge-faq.html#why-setuptools-and-not-distribute-or-another-name

As an addition to fuzzyman's reply:
pip won't install binary packages and isn't well tested on Windows.
As Windows doesn't come with a compiler by default pip often can't be
used there. easy_install can install binary packages for Windows.
Here is a trick on Windows:
you can use easy_install <package> to install binary packages to avoid building a binary
you can use pip uninstall <package> even if you used easy_install.
This is just a work-around that works for me on windows.
Actually I always use pip if no binaries are involved.
See the current pip doku: http://www.pip-installer.org/en/latest/other-tools.html#pip-compared-to-easy-install
I will ask on the mailing list what is planned for that.
Here is the latest update:
The new supported way to install binaries is going to be wheel!
It is not yet in the standard, but almost. Current version is still an alpha: 1.0.0a1
https://pypi.python.org/pypi/wheel
http://wheel.readthedocs.org/en/latest/
I will test wheel by creating an OS X installer for PySide using wheel instead of eggs. Will get back and report about this.
cheers - Chris
A quick update:
The transition to wheel is almost over. Most packages are supporting wheel.
I promised to build wheels for PySide, and I did that last summer. Works great!
HINT:
A few developers failed so far to support the wheel format, simply because they forget to
replace distutils by setuptools.
Often, it is easy to convert such packages by replacing this single word in setup.py.

Just met one special case that I had to use easy_install instead of pip, or I have to pull the source codes directly.
For the package GitPython, the version in pip is too old, which is 0.1.7, while the one from easy_install is the latest which is 0.3.2.rc1.
I'm using Python 2.7.8. I'm not sure about the underlay mechanism of easy_install and pip, but at least the versions of some packages may be different from each other, and sometimes easy_install is the one with newer version.
easy_install GitPython