Develop Reference

Why can I import numpy into my python interpreter but RHEL says numpy not installed?

Per below, rpm tells me numpy isn't installed, yet I have no problem importing numpy into my python interpret. Can anyone explain why that may be? (I had to change the 3 carrots in the interpreter to an arrow for stack to display what happened)
x#red-hat-image install]$ rpm -q numpy
package numpy is not installed
x#red-hat-image yum]$ python
Python 2.7.5 (default, Jun 11 2019, 14:33:56)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-39)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
->import numpy
->

Usually there are three ways to install some package in Linux systems:
Using of OS standard package manager: rpm, yum, apt,... etc
Build it from source using ./confgure and make commands
Using alternative specific package managers: composer or pear for PHP libraries, pip for python libraries,... etc
Sometimes you can install libraries using standard OS package manager. But alternative package managers has own repositories with much more libraries than standard OS repositories. And usually there is newer versions in alter repos.
So using specific language based package managers is a better way.
So rpm command allows you to see only packages installed via standard package manager.
In most cases people using pip manager for python.
So there is high probability that your numpy library was installed via pip.
You can check it using:
# for python2 (or python3 depending on your configuration)
pip freeze | grep numpy
# for python3
pip3 freeze | grep numpy

Python 3.6.5_1 installed in incorrect location (Mac OS)

I install python 3.6.5_1 using
brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/f2a764ef944b1080be64bd88dca9a1d80130c558/Formula/python.r
and get
Warning: python 3.6.5_1 is already installed
The currently linked version is 3.7.3
You can use brew switch python 3.6.5_1 to link this version.
I use brew switch python 3.6.5_1 and get
Cleaning /usr/local/Cellar/python/3.6.5_1
Cleaning /usr/local/Cellar/python/3.7.3
4 links created for /usr/local/Cellar/python/3.6.5_1
Typing which python3, there is no output, which python gives
/usr/local/bin/python
and typing python3 gives
-bash: /usr/local/bin/python3: No such file or directory
typing python gives
Python 2.7.15 (default, Nov 27 2018, 21:24:58)
[GCC 4.2.1 Compatible Apple LLVM 10.0.0 (clang-1000.11.45.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
How do I make sure that the installed python3.6.5_1 is installed at correct location and is the one referred to by python3?
Extra background :
I have been working with OpenCV for around 5 months now, following this installation guide for installing all requirements including python3.6. I was using this version of brew's python instead of mac's one. Recently I had to install FFmpeg, some errors came up, unwittingly I did something (I don't remember, probably unlinked python) and then I wasn't able to install FFmpeg anyway but also this destroyed my workspace. Right now I keep getting the following error everytime I open up terminal:
-bash: /usr/local/bin/python3: No such file or directory
virtualenvwrapper.sh: There was a problem running the initialization hooks.
If Python could not import the module virtualenvwrapper.hook_loader,
check that virtualenvwrapper has been installed for
VIRTUALENVWRAPPER_PYTHON=/usr/local/bin/python3 and that PATH is
set properly.
I tried brew install python3 and that solves the above warning for virtualenvwrapper. But it installs python3.7.3, whereas I need python3.6 for tensor flow etc.

ImportError: No module named 'cv2' Python3

I have such a problem
(face_det) user#pc:~$ python3
Python 3.5.3 (default, Apr 22 2017, 00:00:00)
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named 'cv2
I don't have it on python2:
(face_det) user#pc:~$ python2
Python 2.7.13 |Anaconda custom (64-bit)| (default, Dec 20 2016, 23:09:15)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
Anaconda is brought to you by Continuum Analytics.
Please check out: http://continuum.io/thanks and https://anaconda.org
>>> import cv2
>>>
In spite of the fact, that I have opencv (I've also tryed to remove it and install then):
(face_det) user#pc:~$ pip3 install opencv
Requirement already satisfied: opencv in ./.virtualenvs/face_det/lib/python3.5/site-packages
(face_det) user#pc:~$ conda install opencv
Fetching package metadata .........
Solving package specifications: .
# All requested packages already installed.
# packages in environment at /home/pc/anaconda3:
#
opencv 3.2.0 np112py27_0 conda-forge

Try
pip3 install opencv-python
to get the cv2. I'm not sure when opencv-python became available. I'd been building opencv by hand, but when I looked a few weeks ago, there it was. I'm using cv2 with Python3 in a VM that's running ubuntu/trusty64.

Try
sudo python3.5 -m pip install opencv-python
It worked for me

On Windows you can try this:
python3 -m pip install opencv-python

Your conda openCV is installed for use by your home python2.7. Your opencv installed via pip3 is for use in your face_det virtual environment. It doesn't look like you're in that virtual environment when you opened python3 in the first code block. Try
source activate face_det
python3
import cv2

I think you're on Linux judging by pc:~$
Try installing from the following link:
http://docs.opencv.org/3.0-beta/doc/tutorials/introduction/linux_install/linux_install.html
It worked for me, hope the same for you!

I had a similar problem and the same error. In my case, I was using PyCharm. The problem was that the project's interpreter was pointing to a different installation of Python.
In my system, I had four versions of python (eg. python3 installed in a python36 folder, another python in an anaconda3 folder and others). In my PyCharm project, when I examined my settings (under File->Settings->Project:xxxx ->Project interpreter), I found that they were pointing to the interpreter in the anaconda3 folder.
However, my default pip installed the opencv-python module under the python36 folder. Therefore, I just had to change the project interpreter to point to the python installed in python36 folder and it worked.
If you would like to keep using Anaconda3 then you have to browse to the anaconda3 folder and run pip install opencv-python in that folder.

'setuptools' module not contained in python 3.4?

I was trying to import setuptools in Python3.4 as following,
>>> from setuptools import setup
But I got the ImportError: No module named 'setuptools'.
My current version of Python3.4 is Python 3.4.0b1 (default, Nov 29 2013, 16:37:17), and it is installed using MacPorts.
So there is no setuptools module contained in Python 3.4 Standard Library, right? and I need to install setuptools module through pip?
Update:
setuptools is not in the standard library. But I cannot install it through pip because pip need setuptools installed first. MacPorts contains py34-setuptools #2.0.2 port and I can install setuptools through it.

setuptools has never been a part of the standard lib. You'll always to download it separately.
For 3.4, download setuptools - (This is the compressed download link!), extract it and install it via:
python setup.py install

You'll have to install it yourself. If you've got a completely empty environment in a new python installation, have a look at the official install instructions.

It works for me, but I'm using 3.4b2 on a Linux Mint system:
$ /usr/local/cpython-3.4/bin/python
Python 3.4.0b2 (default, Jan 5 2014, 13:53:24)
[GCC 4.7.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from setuptools import setup
>>>

Installing Pygame for Python 3.1.2 in Ubuntu

I'm reading the book Introduction to Computer Science Using Python and Pygame by Paul Craven (note: legally available for free online). In the book, he uses a combination of Python 3.1.3 and Pygame 1.9.1 . In my Linux Ubuntu machine, I have Python 3.1.2 but even after I sudo apt-get installed python-pygame (version 1.9.1), Python 3.1.2 can't import pygame.
Python 3.1.2 (r312:79147, Sep 27 2010, 09:45:41)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pygame
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named pygame
Python 2.6.5 imports it without fuss, however,
Python 2.6.5 (r265:79063, Apr 16 2010, 13:09:56)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pygame
>>>
Are you aware of any issues for Linux/Ubuntu's Python 3.1.2 (Prof. Craven used Windows in his book)? How come Pygame 1.9.1 worked for Python 3.1.3 but not for 3.1.2?
Thanks for any pointers. (--,)

PyGame on Python 3 remains experimental, but these steps worked for me on Ubuntu 11.10:
sudo apt-get install mercurial python3-dev libjpeg-dev libpng12-dev libportmidi-dev libsdl-image1.2-dev libsdl-mixer1.2-dev libsdl-ttf2.0-dev libsdl1.2-dev libsmpeg-dev libx11-dev ttf-freefont libavformat-dev libswscale-dev
hg clone -u 01b2cb16dc17 https://bitbucket.org/pygame/pygame
cd pygame
python3 config.py
2to3 setup.py -w
python3 setup.py build
sudo python3 setup.py install
(You may remove the -u 01b2cb16dc17 to try the latest version; 01b2cb16dc17 worked for me.)

I hate to re-open an old post, but I had the hardest time installing pygame with a version of python that was not Ubuntu's default build. So I created this tutorial/ how to:
Install python3.1 and pygame1.9.1 in Ubuntu
I hopes this helps the next unfortunate soul to try this.

I installed pygame for python3 quite easily using the pip3 (a tool for installing and managing Python packages) command on Ubuntu 16.04.7 LTS.
Open a terminal and install pip3, type sudo apt install python3-pip
Now use it to install pygame for python3, type pip3 install pygame
That's it! Import the library and confirm that everything works:
# I'll try it out using the python 3 interpreter.
python3 --version
Python 3.5.2
robert#robert-E7212:~/Source/Python/python_crash_course/alien_invasion$ python3
Python 3.5.2 (default, Oct 7 2020, 17:19:02)
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
# No errors, pygame was imported successfully!
>>> import pygame
pygame 2.0.0 (SDL 2.0.12, python 3.5.2)
Hello from the pygame community. https://www.pygame.org/contribute.html
>>>

I followed #Søren 's method, but without the -u number.
The only complication was a few compilation errors at the last line, all due to syntax and unicode differences between Python 2 and Python 3, but with a little checking of the web documentation it was a matter of a few minutes with a text editor modifying the following files (all paths are relative to the pygame directory created during the download):
gedit build/lib.linux-x86_64-3.2/pygame/colordict.py
gedit build/lib.linux-x86_64-3.2/pygame/tests/test-utils/png.py
gedit build/lib.linux-x86_64-3.2/pygame/examples/movieplayer.py
The line numbers from the compiler error messages are great for giving you where to start. The things to look out for are:
1 remove all references to u"xxxx" colours
2 use Python3 syntax for exceptions
3 change all print commands to Python3 equivalents
Then re-issue the final compilation command:
sudo python3 setup.py install
If you miss one or two or get it wrong, just keep going round the loop editing and re-compiling till it works.
BTW I deliberately did not give details of the compiler messages, because I expect they will depend on the current build you download. The files I needed to change were for version '1.9.2pre' downloaded as of the date on this post.

Just use the below command to install pygame for Python3. I could install pygame correctly on Ubuntu 16.04 and Python Python 3.5.2.
pip3 install pygame

It's because installing the python-pygame package installs it for the default version of Python on your system, 2.6.5 in this case. You should download the pygame package and use setup.py to install it in 3.1.2.

The python-pygame package is only compiled for python2.6 and python2.7 where I am. You'll have to install it again, possibly from a python3 branch of the source.