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The accepted answer is outdated.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.

How to install Numpy & pip3 for python3.x when they were installed in python2.7? Using Conda?

I want to write program in python3 (3.5), hence I installed python3 next to the pre-installed python2 (2.7) on Mac OS X El Captian.
Since my terminal runs python2.7 by default and Numpy is already installed for it, I put alias python=python3 and expected to be able to install Numpy for python3. when I type pip install numpy. This was the generated message:
Requirement already satisfied (use --upgrade to upgrade): numpy in /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages
I also noticed that I have no pip3 even though I am using python3: python --version returned Python 3.5.2, but pip3 install numpy got me -bash: pip3: command not found.
So my questions are:
1) How to install Numpy for python3.x when Numpy is installed on python2.x?
2) How to get pip3?
3) Is it better to use virtual environments, such as Conda, instead of juggling between python2 and python3 on the system?
Thank you from a total n00b
------------------- Update -------------------
Reinstalling python3 also fixed another problem in my case.
When I ran brew doctor, one of the warning message I got was:
Warning: You have unlinked kegs in your Cellar Leaving kegs unlinked can lead to build-trouble and cause brews that depend on those kegs to fail to run properly once built. Run brew link on these: python –
This is a result of me running brew unlink python in order to fix
"Python quit unexpectedly"
when I launch Vim and also
"The ycmd server SHUT DOWN"
Both seem to relate to the YouCompleteMe autocomplete plugin which I downloaded for Python.
I got my idea of removing symlinks from here and here
However, Homebrew evidently did not like the absence of those 39 symlinks.
After uninstall (brew uninstall python3) and then re-install python3 (brew install python3) as Toby suggested, Homebrew gave me
You can install Python packages with
pip3 install <package>
Then when I pip3 install numpy and pip3 install scipy, both executed successfully.
To my surprise, symlinks created during Python installation used to cause aforementioned error messages for Python and YouCompleteMe, but now I open python files using Vim without crash from a fresh Python installation, which definitely created the symlinks.
------------------- Update2 ------------------
After re-installing Anaconda2, the same YouCompleteMe error came back. I suspect Anaconda messed up symlinks.

I would recommend using the Anaconda Python distribution.
The main reasons are as such:
You will have a Python distribution that comes with numpy and the rest of the Scientific Python stack.
The Anaconda Python will be installed under your home directory, with no need for sudo-ing to install other packages.
conda install [put_packagename_here] works alongside pip install [put_packagename_here]; conda install is much 'cleaner' (IMHO, differing opinions are welcome).
If you have a Python 3 environment as your default, then pip works out-of-the-box without needing to remember to do pip3.
conda environments are easier to manage than virtualenv environments, in my opinion. And yes, you can have Python 2 alongside Python 3.
I once messed up my system Python environment - the one that came with my Mac - and it broke iPhoto (back in the day). Since then, I became convinced of needing separate, atomic environments for different projects.
I've detailed more reasons in a personal blog post.
Other distributions, of course, are all good, provided they give you what you need :).

The simplest way on a Mac is with Homebrew:
http://brew.sh/
Install Homebrew, then run:
brew install python3 pip3
Edit --
Python3 includes pip3, but Homebrew occasionally has trouble linking to the correct versions, depending on what has been installed. Running the following command:
brew doctor
And if you see errors relating to python or unlinked kegs, try running:
brew uninstall python python3
And reinstalling after checking brew doctor.
https://unix.stackexchange.com/questions/233519/pip3-linked-to-python-framework-instead-of-homebrew-usr-local-bin

How to properly install wxPython?

So I was looking around at different things to do on Python, like code for flashing text or a timer, but when I copied them into my window, there were constant syntax errors. Now, maybe you're not meant to copy them straight in, but one error I got was 'no module named wx'. I learned that I could get that module by installing wxPython. Problem is, I've tried all 4 options and none of them have worked for me. Which one do I download and how do I set it up using Windows?
Thanks

It's on PyPI. As of wxPython 4, Python 3 is supported.
Unfortunately, PyPI has a package called wx that is stuck at version 3.0.3; be sure to install the package named wxpython instead.
pip install wxpython
Please note that pip will automatically build wxWidgets for you, but it will not install wxWidgets system dependencies such as GTK and OpenGLu. If the above command exits with an error, look above for a message like this:
checking for <something>... not found
checking for <something>... no
configure: error: <prereq> libraries not available
Error running configure
ERROR: failed building widgets
This should give you information about at least one of the packages your system is missing.
The "official" list of prerequisites from the wxWidgets source is:
dpkg-dev
build-essential
libjpeg-dev
libtiff-dev
libsdl1.2-dev
libgstreamer-plugins-base0.10-dev # or 1.0 if available
libnotify-dev
freeglut3
freeglut3-dev
libsm-dev
libgtk-3-dev
libwebkitgtk-3.0-dev # or libwebkit2gtk-4.0-dev if available
libxtst-dev
The actual package names provided by your package manager may not match these exactly, and to be honest, I don't really know the best way to query a package manager to determine what packages provide the libraries you need.

3 steps to install wx-widgets and pygame in python IDLE
Install python 3xxx in your system opting (Add 3xxx to your path).
open python CLI to see whether python is working or not.
then open command prompt (CMD).
type PIP to see whether pip is installed or not.
enter command : pip install wheel
enter command : pip install pygame
To install wxpython
enter command : pip install -U wxPython
Thats all !!

As per home page instruction:
Make sure you have at least version 6.0.8 of pip and 12.0.5 for setuptools.
Install requirements for Linux as outlined in the readme.rst at:
https://github.com/wxWidgets/Phoenix/blob/master/README.rst
Install wxPython-Phoenix (Linux):
sudo pip install --upgrade --trusted-host wxpython.org --pre -f http://wxpython.org/Phoenix/snapshot-builds/ wxPython_Phoenix
Install wxPython-Phoenix (Windows, use the appropriate script folder):
C:\python27\scripts\pip.exe install --upgrade --trusted-host wxpython.org --pre -f http://wxpython.org/Phoenix/snapshot-builds/ wxPython_Phoenix

I installed wxPython as part of the PsychoPy experiment builder dependencies, and had considerable trouble getting it to install properly as well initially. But this was what worked for me at the end. I use Ubuntu 16.04, python 3.5, pip3 19.0.3
pip3 install -U -f https://extras.wxpython.org/wxPython4/extras/linux/gtk3/ubuntu-16.04 wxPython --user

If you use Conda then you may easily setup the environment with wx by one line:
$ conda create -n wxenv python=3 wxPython
Solving environment: done
## Package Plan ##
environment location: /home/user/.conda/envs/wxenv
added / updated specs:
- python=3
- wxpython
The following packages will be downloaded:
package | build
---------------------------|-----------------
[...]
Proceed ([y]/n)?

You need to ensure the versions of your wxPython download matches your installed python language library.
The current downloads wxPython downloads doesn't show any libraries built against python 3. I Believe the python 3 porting project is still ongoing.
If you are not sure of what you are doing I would stick with the 32bit version on windows as there are some Python libraries (ie IIRC, MySQLdb) which don't work with 64 bit python.
So you would then need to download python2.7 for windows x86 and "wxPython3.0-win32-py27 32-bit Python 2.7"

To install wxPython GUI library correctly go to the following page (https://wxpython.org/Phoenix/snapshot-builds/), which contains snapshots builds of wxPython library (Phoenix version) depending on your os and version of Python you want to work.
Then when you downloaded the proper package for your system and python version, simply install it by using pip. In my case I've choosen that one (wxPython_Phoenix-3.0.3.dev2811+ecc4797-cp36-cp36m-win_amd64.whl):
pip install wxPython_Phoenix-3.0.3.dev2811+ecc4797-cp36-cp36m-win_amd64.whl
To check that it has been installed sucessfully on the site-packages folder for your current python environment write:
pip freeze
It's all!

Check the version of wxpython and the version of python you have in your machine.
For python 2.7 use wxPython3.0-win32-3.0.2.0-py27 package

The problem was solved in openSuse simply with
zypper in python-wxWidgets-3_0-devel
Trying pip install before, gave me a lot of trouble (missing traits, missing wx/setup.h, https://github.com/wxWidgets/Phoenix/issues/1644, error: aggregate ‘wxGLAttributes _NullGLAttributes’ has incomplete type and cannot be defined, etc.).

wxpython failed to be installed with pipenv. Pipenv is not able to find wxpython binary so it tries to build wxpython but fails.
CXXFLAGS="-I/opt/homebrew/include" pipenv install wxpython
On my macOS M1 pipenv failed to install wxPython. After a lot of searching I found a forum post which really helped me fix the problem.
Source/Credits: https://forums.wxwidgets.org/viewtopic.php?t=47953&p=203709

Install current development version with:
pip install -U https://github.com/robotframework/RIDE/archive/master.zip
(python < 3.9) Install current Beta version (2.0b1) with:
pip install psutil
pip install -U --pre robotframework-ride

Note that I tried to install wxPython with 'pip install -U wxPython' as per instruction
with no avail. Too many errors to list here. 🤨
I found a solution to the problem!!
I'm working on a 64b machine and Windows 11 operating system using VSCode.
Here is the solution using PowerShell:
Version specs:
pip 22.3.1
virtualenv 20.15.1
python 3.10.8
Create a new virtual environment in the directory where the program resides and
activate. There must be no modules installed.
virtualenv venv
venv/scripts/activate.bat
Install the following in sequence:
pip install pygame
(Not sure why pygame must be installed first, but this was
recommended and it works) 😟
pip install -U wxPython
SUCCESS!!! 🤠
These are the modules installed:
numpy 1.24.1
Pillow 9.4.0
pip 22.3.1
pygame 2.1.2
setuptools 65.4.0
six 1.16.0
wheel 0.37.1
wxPython 4.2.0
VSCode still reports wx as a missing module even when you activate the virtual
environment within. Running the code from the PS command prompt within the virtual
environment is the only working solution.
PS. I am sure there are some conflicts when trying to install wxPython within an
environment where all the other modules are installed.

Installing numpy for Python 2.7 while also having Python 3.4 installed?

I have both Python 2.7 and Python 3.4 (and have to have both because for the class I'm running, students have the option of using either). One student has used Python 2.7 and numpy for their project, but when I attempt to install numpy, it installs it to 3.4. I need to install it to 2.7.
I'm using numpy 1.9 from this site, which I'm told is also 2.7-specific: http://sourceforge.net/projects/numpy/files/NumPy/
However, nonetheless it still goes to the 3.4 folder. Copying it to Python 2.7 didn't work, obviously.
How do I do this?

I recommend installing with pip.
pip install numpy
If this doesn't work on windows then download the binary from http://www.lfd.uci.edu/~gohlke/pythonlibs/ and convert it to a wheel before installing.
pip install wheel
wheel convert path/to/binary
pip install numpy_wheel
Pip is recommended because you can uninstall.
To check where you are installing to
pip -V
You may have an environmental variable path to the wrong pip.

Assuming that you are using, or at least you should use pip to install the library. You can specify the python version to be installed by changing the suffix, e.g. pip-2.7 install numpy.
pip install numpy
pip-2.7 install numpy
pip-3.4 install numpy
As an alternative, in case that you do not want to use pip is to download and install the library using setup with a similar technique.
python setup.py install
python2.7 setup.py install
python3.4 setup.py install

Your PATH isn't setup correctly.
C:> where pip
Should tell you which pip it is trying to use, and it is likely whichever one it found on your PATH first...
So, instead, you will want to run it as
C:> C:\mypython2install\pip.exe install numpy
Or, setup your path correctly. See here

Just one other note on issues like this. I had a similar problem with Python 2.7 libraries not being found, because I had miniconda installed for a Python virtual environment that was hijacking calls to python from other programs. After deleting the minconda directory in my home the problem went away and python libraries that were properly installed were found again.

Note-This answer is particularly for Windows PC which has both Python2 & Pyhton3 installed on it.
Both the versions of Python has their different directories somewhat like
"C:\Python27\" ----for python2
"C:\Python35\" ---- for python3
*(or it depends on what path you chose while installing Python**)*
pip GENERALLY exist under the directory "C:\Python**\Scripts"
there you can find exe files like:
pip.exe/pip2.exe/pip2.7.exe ----for python2
pip3.exe/pip3.5.exe ----for python3
to install packages on python2:
use
Python27\Scripts\pip2.exe install package_name
(where the 1st argument is the path of exe file, it might differ for your system)
to install packages on python3:
use
Python35\Scripts\pip3.exe install package_name
there is no need to uninstall any version of python to achieve the task.

What is causing ImportError: No module named pkg_resources after upgrade of Python on os X?

I just updated Python to 2.6.4 on my Mac.
I installed from the dmg package.
The binary did not seem to correctly set my Python path, so I added '/usr/local/lib/python2.6/site-packages' in .bash_profile
>>> pprint.pprint(sys.path)
['',
'/Users/Bryan/work/django-trunk',
'/usr/local/lib/python2.6/site-packages',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python26.zip',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-darwin',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/plat-mac/lib-scriptpackages',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-tk',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-old',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/lib-dynload',
'/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages']
Apparently that is not all the required paths because I can't run iPython.
$ ipython
Traceback (most recent call last):
File "/usr/local/bin/ipython", line 5, in <module>
from pkg_resources import load_entry_point
ImportError: No module named `pkg_resources`
I've done Google searches and I can't really figure out how to install pkg_resources or make sure it's on the path.
What do I need to do to fix this?

I encountered the same ImportError. Somehow the setuptools package had been deleted in my Python environment.
To fix the issue, run the setup script for setuptools:
curl https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py | python
If you have any version of distribute, or any setuptools below 0.6, you will have to uninstall it first.*
See Installation Instructions for further details.
* If you already have a working distribute, upgrading it to the "compatibility wrapper" that switches you over to setuptools is easier. But if things are already broken, don't try that.

[UPDATE] TL;DR pkg_resources is provided by either Distribute or setuptools.
[UPDATE 2] As announced at PyCon 2013, the Distribute and setuptools projects have re-merged. Distribute is now deprecated and you should just use the new current setuptools. Try this:
curl -O https://bitbucket.org/pypa/setuptools/raw/bootstrap/ez_setup.py
python ez_setup.py
Or, better, use a current pip as the high level interface and which will use setuptools under the covers.
[Longer answer for OP's specific problem]:
You don't say in your question but I'm assuming you upgraded from the Apple-supplied Python (2.5 on 10.5 or 2.6.1 on 10.6) or that you upgraded from a python.org Python 2.5. In any of those cases, the important point is that each Python instance has its own library, including its own site-packages library, which is where additional packages are installed. (And none of them use /usr/local/lib by default, by the way.) That means you'll need to install those additional packages you need for your new python 2.6. The easiest way to do this is to first ensure that the new python2.6 appears first on your search $PATH (that is, typing python2.6 invokes it as expected); the python2.6 installer should have modified your .bash_profile to put its framework bin directory at the front of $PATH. Then install easy_install using setuptools following the instructions there. The pkg_resources module is also automatically installed by this step.
Then use the newly-installed version of easy_install (or pip) to install ipython.
easy_install ipython
or
pip install ipython
It should automatically get installed to the correct site-packages location for that python instance and you should be good to go.

In case of upgrading your python on mac os 10.7 and pkg_resources doesn't work, the simplest way to fix this is just reinstall setuptools as Ned mentioned above.
sudo pip install setuptools --upgrade
or sudo easy_install install setuptools --upgrade

On my system (OSX 10.6) that package is at
/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py
I hope that helps you figure out if it's missing or just not on your path.

The reason might be because the IPython module is not in your PYTHONPATH.
If you donwload IPython and then do
python setup.py install
The setup doesn't add the module IPython to your python path.
You might want to add it to your PYTHONPATH manually. It should work after you do :
export PYTHONPATH=/pathtoIPython:$PYTHONPATH
Add this line in your .bashrc or .profile to make it permanent.

I realize this is not related to OSX, but on an embedded system (Beagle Bone Angstrom) I had the exact same error message. Installing the following ipk packages solved it.
opkg install python-setuptools
opkg install python-pip

I got this error on Ubuntu, and the following worked for me:
Removed the dropbox binaries and download them again, by running:
sudo rm -rf /var/lib/dropbox/.dropbox-dist
dropbox start -i

I encountered with the same problem when i am working on autobahn related project.
1) So I download the setuptools.-0.9.8.tar.gz form https://pypi.python.org/packages/source/s/setuptools/ and extract it.
2 )Then i get the pkg_resources module and copy it to the folder where it needed.
**in my case that folder was C:\Python27\Lib\site-packages\autobahn

In my case, package python-pygments was missed. You can fix it by command:
sudo apt-get install python-pygments
If there is problem with pandoc. You should install pandoc and pandoc-citeproc.
sudo apt-get install pandoc pandoc-citeproc

Try this only if you are ok with uninstalling python.
I uninstalled python using
brew uninstall python
then later installed using
brew install python
then it worked!