I have python installed, python 3 installed, installed opencv using homebrew, also installed python through the GUI, followed various instructions pages and comments written several years ago.
I'd like to use OpenCV to detect brightest and darkest pixels and draw line between them to carve the image up into cells based on the bright and dark points in each cell. I assume this a reasonable application for this software.
When I go to python, any installation, and enter import cv I get a 'no module' message.
First, you need to decide whether you want to run Python2 or Python 3. I would advocate Python 3, firstly because this is clearly a new project so you may as well use the latest and greatest Python, and secondly since Python 2 is end-of-lifed in 9 days' time.
Then you need to decide if you want to use the Apple-supplied Python, in /usr/bin or the homebrew supplied Python. As you have installed homebrew Python, I would advocate using the homebrew one because you can delete the whole thing and re-install it if you mess it up while all the Apple-supplied patches, OS upgrades and their other uses of their Python will remain unaffected. Happy days!
So, you want to use homebrew Python 3. Now check what homebrew tells you, by running:
brew info python
Unversioned symlinks python, python-config, pip etc. pointing to
python3, python3-config, pip3 etc., respectively, have been
installed into /usr/local/opt/python/libexec/bin
That means if you want to run python and pip (without a version number, as opposed to python3 and pip3) and expect that to start Python 3 and its corresponding pip, you need to put /usr/local/opt/python/libexec/bin at the start of your PATH in your bash profile (probably $HOME/.bash_profile):
export PATH=/usr/local/opt/python/libexec/bin:$PATH
Then start a new Terminal and check which Python runs when you type python:
type python
And it must report as follows if you are on the right track:
python is /usr/local/opt/python/libexec/bin/python
Then, you can check which Python version that is with:
python -V
and it should be:
Python 3.7.5
Now you can install OpenCV with:
pip install opencv-python
Then load it in the interpreter with:
import cv2
If, for some reason, you want to run the old v2.7 Python, or risk messing up the installation of your macOS by installing clashing modules, just disregard my answer.
Related
Background
Currently, I have Python 2.7.17 and Python 3.8.1 installed on my Mac (v 10.14.6). Both Python versions were downloaded directly from Python.org using a "macOS 64-bit installer" .pkg file, in late 2019. Both were installed here:
python2: /Library/Frameworks/Python.framework/Versions/2.7/bin/python2
python3: /Library/Frameworks/Python.framework/Versions/3.8/bin/python3
Currently, I use only pip (either pip2 or pip3, depending) to install python packages, which are saved here:
python2: /Library/Frameworks/Python.framework/Versions/X.X/lib/python2.7/site-packages
python3: /Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages
I am about to begin an online course which requires that I install miniconda in order to install the packages that I need for the course. But after having a very bad experience having Anaconda installed on my machine years ago, and it taking me months to remove it and re-create a clean Python install, I am nervous. I don't want my machine to become a mess again, rife with error messages that it can't find this or that python version or this or that python library.
Question(s)
Assuming there will now be multiple installations of Python on my machine (in addition to the versions that I already have, since I believe yet another version of python is installed along with conda), and there will be new places where python packages will be saved, what can I expect to change about how I write python after I install miniconda?
Is there anything I will need to do differently from what I am doing now when I write python code?
How can I ensure that everything remains working and compatible and I avoid the fate I suffered many years ago?
Happy to edit/clarify this question per user suggestions. Thanks!
Use conda environments and install Python into those environments. This ignores, by design, the versions of Python that are installed at the system level. Also, what's installed into environments (other than the one you're in) is ignored. As somebody who uses conda for all Python development, I don't even know what I have installed in /usr/local/bin/ or other places. Everything is in /path/to/miniconda3/envs/env_name_n. You don't have to uninstall other versions of Python you have elsewhere; the point of environments is to keep everything isolated.
What can I expect to change about how I write python after I install miniconda?
Is there anything I will need to do differently from what I am doing now when I write python code?
Use conda environments and use conda as your package manager. For almost every major project, it nearly a drop-in replacement for pip. Outside of managing dependencies, not much changes.
thanks for reading this. I am using macOS High Sierra. I am not very familiar with terminal or environment variables, but am trying to learn more. From reading other threads and google, it seems like I either have multiple pythons installed, or have pythons running from different paths. However I am not able to find a solution to resolving this, either by re-pathing my IDLE or deleting it entirely.
I do have python, python launcher, and anaconda (not very sure how anaconda works, have it installed a few years back and didn't touch it) installed. I am trying to install pandas (pip install pandas), which tells me that I have it installed, but when I run it on IDLE, it says module not found. Though if i run python3 on terminal and type my code in, it works (so pandas has indeed been installed).
When i run which python on terminal, it returns
/Users/myname/anaconda3/bin/python
(when i enter into this directory from terminal, it shows that in the bin folder, I have python, python.app, python3, python3-config, python3.7, python3.7-config, python3.7m, python3.7m-config)
When i run which idle on terminal, it returns
/usr/bin/idle (im not even sure how to find this directory from the terminal)
When i run import os; print(os.path) on IDLE, it returns module 'posixpath' from '/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/posixpath.py'
Would really appreciate some help to figure out how to ensure that when i install modules from terminal, it would be installed into the same python as the one IDLE is using. Also, I would like to know whether it is possible for me to work on VSCode instead of IDLE. I cant seem to find suitable extensions for data science and its related modules (like statsmodels, pandas etc). Thanks a lot!
First of all, a quick description of anaconda:
Anaconda is meant to help you manage multiple python "environments", each one potentially having its own python version and installed packages (with their own respective versions). This is really useful in cases where you would like multiple python versions for different tasks or when there is some conflict in versions of packages, required by other ones. By default, anaconda creates a "base" environment with a specific python version, IDLE and pip. Also, anaconda provides an improved way (with respect to pip) of installing and managing packages via the command conda install <package-name>.
For the rest, I will be using the word "vanilla" to refer to the python/installation that you manually set up, independent of anaconda.
Explanation of the problem:
Now, the problem arises since you also installed python independently. The details of the problem depend on how exactly you set up both python and anaconda, so I cannot tell you exactly what went wrong. Also, I am not an OSX user, so I have no idea how python is installed and what it downloads/sets alongside.
By your description however, it seems that the "vanilla" python installation did not overwrite neither your anaconda python nor anaconda's pip, but it did install IDLE and set it up to use this new python.
So right now, when you are downloading something via pip, only the python from anaconda is able to see that and not IDLE's python.
Possible solutions:
1. Quick fix:
Just run IDLE via /Users/myname/anaconda3/bin/idle3 every time. This one uses anaconda's python and should be able to see all packages installed via conda install of pip install (*). I get this is tiresome, but you don't have to delete anything. You can also set an "alias" in your ~/.bashrc file to make the command idle specifically linking you there. Let me know with a comment if you would like me to explain how to do that, as this answer will get too long and redundant.
2. Remove conda altogether (not recommended)
You can search google on how to uninstall anaconda along with everything that it has installed. What I do not know at this point is whether your "vanilla" python will become the default, whether you will need to also manually install pip again and whether there is the need to reinstall python in order for everything to work properly.
3. Remove your python "vanilla" installation and only use anaconda
Again, I do not know how python installation works in OSX, but it should be reasonably straightforward to uninstall it. The problem now is that probably you will not have a launcher for IDLE (since I am guessing anaconda doesn't provide one on OSX) but you will be able to use it via the terminal as described in 1..
4. Last resort:
If everything fails, simply uninstall both your vanilla python (which I presume will also uninstall IDLE) and anaconda which will uninstall its own python, pip and idle versions. The relevant documentation should not be difficult to follow. Then, reinstall whichever you want anew.
Finally:
When you solve your problems, any IDE you choose, being VScode (I haven't use that either), pycharm or something else, will probably be able to integrate with your installed python. There is no need to install a new python "bundle" with every IDE.
(*): Since you said that after typing pip install pandas your anaconda's python can import pandas while IDLE cannot, I am implying in my answer that pip is also the one that comes with anaconda. You can make sure this is the case by typing which pip which should point to an anaconda directory, probably /Users/myname/anaconda3/bin/pip
First: This would be a comment if I had enough reputation.
Second: I would just delete python. Everything. And reinstall it.
To repeat and summarized what has been said on various other question answers:
1a. 3rd party packages are installed for a particular python(3).exe binary.
1b. To install multiple packages to multiple binaries, see the option from python -m pip -h.
To find out which python binary is running, execute import sys; print(sys.executable).
3a. For 3rd party package xyz usually installed in some_python/Lib/site-packages, IDLE itself has nothing to do with whether import xyz works. It only matters whether xyz is installed for 'somepython' (see 1a).
3b. To run IDLE with 'somepython', run somepython -m idlelib in a terminal or console.
somepython can be a name recognized by the OS or a path to a python executable.
Using Ubuntu 16.04.
I was doing development in Python2.7, although recently moved to Python3.5, both of which come by default. The problem is, I find all the python libraries have to be reinstalled or downloaded for the next Python3. Also, the behaviour of Python seems weird because to execute the same script in python3, I have to enter in terminal
python3 script.py
which is different from other applications where I do not have to give the version number. Anyway, the questions I am trying to find answers are
To what extent are the libraries, packages (such as pip etc.) shared between 2.7 and 3.5? Or do I need double installations (and double the space) for everything now? A bit space limited in my old laptop.
Most of the installation instructions and commands I find online do not specify whether they are for 2 or 3. Given that I have two versions, how do I control/make sure they go to 3.5?
Is it advisable and possible to completely remove everything related to 2.7? Can I keep working with 3.5?
The first thing you need to know is that all official libraries and python tools for python3 got the "3" character to separate them from the previous versions. So, you need to use pip3, and not pip, python3, not python, and the packages are called python-pygame, not python-pygame.
So, to answer to you in order:
Yes, the you have to double the space needed if you decide to use both python2 and python3
Usually, if in the tool name there is 3, it is for python3, and if not it's for python2
Python2 and python3 are completly indipendent (different path, indipendent versions, etc.) so having python 2.7 installed doesn't affect python3 BUT since python 3 is the next version of python 2, it makes it obsolete (in my opinion) so if you don't have enough space for both, keeping python2 is absolutely not needed nor useful
If you want to control your python execution then you have various method or techniques:
For downloading packages according to version
You can use pip{version-name} to download the libraries. Like if you want to download library of python 2.7 then write
pip2.7 install package-name
for python 3.5 then use
pip3.5 install package-name
For execution of program:
If you want to execute the program accoridng to you choice of version then just use
python{version-name} script.py
eg:
python2 script.py
python3 script.py
or you just write down the path of your python version on the top of script. Please refer this for more details:
Why do people write #!/usr/bin/env python on the first line of a Python script?
Recently I've installed Python 3 after using 2 for quite a while, so I have many libraries for Python that I've installed using pip. I've already started using the symlink python3, but what else do I need to do to change over?
For example, while I have made the alias python=python3, I don't know about the modules I've installed with pip. I was using a version of pip for Python 2, but does that mean modules were written for Python 2 and not 3? Do I now need to start using pip3 (or make a corresponding alias pip=pip3 or pip=pip3.5)? If modules were installed using the command pip, does that mean I have to reinstall them for Python 3 using pip3? If I do need to reinstall them for 3, should I start removing them from my Python 2 env as cleanup?
And another question that seems like it may entail a lot of work: How should I change all my virtual environments for Python projects? They were all Python 2 envs, and now I'm not sure whether it's necessary, useful, or possible to reinstall or upgrade the modules within them to the corresponding ones for Python 3.
Sorry if this seems like a duplicate question - I've searched and only found resources regarding "how to upgrade" rather than "what to do after upgrading". Thanks for your help!
It is strongly recommended not to symlink python to Python 3, at least on Debian-based Linux distros. Debian utility scripts use both Python 3 and 2.7 to work (which means you already had a copy of Python 3 somewhere...), and as a consequence Debian-based distributions ship both versions. Symlinking can cause unexpected breakages. This may or may not be true on other systems, however, but with such ambiguity it is probably useful not to try.
Instead, live with symlinking python3 to Python 3. Leave python alone.
pip is usually symlinked to the corresponding pip program for 2.7. Use pip3 to specify you want to use the pip program for Python 3. If you use pip, you'll find modules for Python 3 being installed to Python 2.7 site directories and nothing will work as you expect it to. There should be no reason why you can't symlink pip to pip3, but I'd still not recommend it - it's better to tread cautiously in this regard.
You don't need to change your current virtual environments. Just create new ones with virtualenv, pointing to the correct Python program to use. This is the whole point of virtual environments: to sandbox different Python versions, so that neither of them adversely interact with each other.
If you have projects you really want to ship to Python 3, I'd recommend using a version control system to back up your current files, and then reproducing them in a new virtual environment configured for Python 3. This is quick, simple and painless.
I new to Python and to programming in general. I'm a novice, and do not work in programming, just trying to teach myself how to program as a hobby. Prior to Python, I worked with Ruby for a bit and I learned that one of the biggest challenges was actually properly setting up my computer.
Background: I'm on a Macbook with OSX 10.7.
With Ruby, you have to (or rather, you should), edit your ./profile and add PATH info. When you install and use RVM, there are additional items you need to add to your bash_profile.
Do you have to make similar changes with Python? What are the best practices as I'm installing/getting started to ensure I can install modules and packages correctly?
python works out of the box on OS X (as does ruby, for that matter). The only changes I would recommend for a beginner are:
1) Python likes to be reassured that the terminal can handle UTF-8 before it will print Unicode strings. Add export LANG=en_US.UTF-8 to .profile. (It may be that the .UTF-8 part is already present by default on Lion - I haven't checked since Snow Leopard.) Of course, this is something that will help you in debugging, but you shouldn't rely on it being set this way on other machines.
2) Install pip by doing easy_install pip (add sudo if necessary). After that, install Python packages using pip install; this way, you can easily remove them using pip uninstall.
Take a loot at Python on the Macintosh page first. Like it says, Python comes pre-installed on Mac OS X. It means that you don't have to do anything special in order to use it.
To get started, you can run a Terminal.app, type python and that will get you Python interactive shell up and running.
However, Python on OS X might be of a slightly older version. For example, OS X 10.7.3 comes with Python 2.7.1, whereas latest release version of the Python is 3.2.3. If you want to use other versions, then you will have to install them. Then it all depends on what, where and how you install. If you want to have multiple versions alongside, you may need to set some environment variables like PATH to have binaries you installed found by the bash etc. You can do it through bash ~/.profile if needed.
But until you get to that point - don't worry about it use a version shipped with OS X. Once you want a newer one - download and install it. Then, if it doesn't work out of the box or you have any other problems or concerns, feel free to ask a more specific question.