As I understood, I have two versions of python 2.7 installed on my machine. One is located in /usr/bin and another one is in /usr/local/bin. When I type python in the shell, it calls one in /usr/local/bin, and it doesn't have access to all the packages installed using apt-get and pip. I have tried to set up an alias, but when I type sudo python it still calls one in /usr/local/bin. I want to always use one in /usr/bin, since I have all the packages there. How do I do that?
From what I understood,
You have two version of python. One is in /usr/local/bin/python
and another is in /usr/bin/python.
In your current configuration default python ->
/usr/local/bin/python
You want to use the one that is in /usr/bin.
Update your ~/.bashrc and append this line at the end
alias python=/usr/bin/python
Then open a new terminal. Or do source ~/.bashrc in the current terminal
Run which python to see the location of the python executable. It will show you /usr/bin/python
Also, if you want to get packages in your current python (i.e. /usr/local/bin/python) you can use pip with that particular python version.
Find pip location using which pip
Assuming pip location is /usr/local/bin/pip
/usr/local/bin/python /usr/local/bin/pip install
you can easily have two python version in your machine.
But first I recommend to install the Anaconda package.
And then you can create an environment with python 3 version
conda create --name test_env python=3 numpy pandas
In order to activate it, you need to write in your terminal
source activate test_env
More info here:
https://conda.io/docs/using/envs.html
Related
I'm using Ubuntu 19.10, in which there is python of version 3.7. After the release of python 3.8, which I have installed, now I want to uninstall python 3.7 so that whenever I would call python3 in my terminal, it would always call python3.8?
You do not need to uninstall old version for this.
You need to update your update-alternatives , then you will be able to set your default python version.
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.4 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.6 2
Then run :
sudo update-alternatives --config python
Set python3.6 as default.
Or use the following command to set python3.6 as default:
sudo update-alternatives --set python /usr/bin/python3.6
This should do it.
I suggest you do not touch your default OS python instalation. Other parts of the system may depend on it and there is no way to know if an upgrade can break something, even if it should not.
I also suggest that you learn (if you haven't already, but I suppose you did not because of the question) about using a python virtual environment, like virtualenv. This allows you to setup specific python environments for each project you write. This means each environment can have its own python version, and, besides the standard python lib for that version, any other third-party python lib you would like to install with pip for that project. This isolates projects from each other. You won't break one because of an upgrade of another.
That said, if you want to keep cutting edge with Python versions, make an install from source, and then install it in the system with the altinstall parameter (see the README.rst of the Python distribution. This way all the installed versions are available with different names (the same for pip) and then you create each of your virtual environments with the wanted version. There is a parameter for virtualenv to apply a specific (older) version if you want.
Quoting the README on the "Installing multiple versions" section:
On Unix and Mac systems if you intend to install multiple versions of Python
using the same installation prefix (--prefix argument to the configure
script) you must take care that your primary python executable is not
overwritten by the installation of a different version. All files and
directories installed using make altinstall contain the major and minor
version and can thus live side-by-side. make install also creates
${prefix}/bin/python3 which refers to ${prefix}/bin/pythonX.Y. If you
intend to install multiple versions using the same prefix you must decide which
version (if any) is your "primary" version. Install that version using make
install. Install all other versions using make altinstall.
For example, if you want to install Python 2.7, 3.6, and 3.8 with 3.8 being the
primary version, you would execute make install in your 3.8 build directory
and make altinstall in the others.
Finally, the other answers are ok to do exactly what you asked, if you still want to.
so that whenever I would call python3 in my terminal, it would always call python3.8
You can simply create an alias for Python 3.8 in your .bashrc file in your /home path.
Open ~/.bashrc with your preferred editor, and go to the last line.
Append this line:
alias python='python3.8'
And whenever you call python in your terminal, it opens Python 3.8.
Note: This doesn't work as expected when creating virtual environments with specific version. You might want to keep that in mind.
What I'm trying to do here is to make python3 as my default python. Except the python 2.7 which automatically installed on mac, I installed python3 with homebrew. This is the website that I'm following. http://docs.python-guide.org/en/latest/starting/install3/osx/#install3-osx
I guess I followed every instruction well, got xcode freshly installed, Command line tools, and homebrew. But here's my little confusion occurs.
The script will explain what changes it will make and prompt you before the installation begins. Once you’ve installed Homebrew, insert the Homebrew directory at the top of your PATH environment variable. You can do this by adding the following line at the bottom of your ~/.profile file
export PATH=/usr/local/bin:/usr/local/sbin:$PATH
I was really confused what this was, but I concluded that I should just add this following line at the bottom of ~/.profile file. So I opened the ~/.profile file by open .profile in the terminal, and added following line at the bottom. And now it looks like this.
export PATH=/usr/local/bin:/usr/local/sbin:$PATH
# Setting PATH for Python 3.6
# The original version is saved in .profile.pysave
export PATH=/usr/local/bin:/usr/local/sbin:$PATH
And then I did brew install python, and was hoping to see python3 when I do python --version.
But it just shows me python 2.7.10. I want my default python to be python3 not 2.7
And I found a little clue from the website.
Do I have a Python 3 installed?
$ python --version
Python 3.6.4
If you still see 2.7 ensure in PATH /usr/local/bin/ takes pecedence over /usr/bin/
Maybe it has to do something with PATH? Could someone explain in simple English what PATH exactly is and how I could make my default python to be python3 when I run python --version in the terminal?
Probably the safest and easy way is to use brew and then just modify your PATH:
First update brew:
brew update
Next install python:
brew install python
That will install and symlink python3 to python, for more details do:
brew info python
Look for the Caveats:
==> Caveats
Python has been installed as
/usr/local/bin/python3
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
Then add to your path /usr/local/opt/python/libexec/bin:
export PATH=/usr/local/opt/python/libexec/bin:$PATH
The order of the PATH is important, by putting first the /usr/local/opt/python/libexec/bin will help to give preference to the brew install (python3) than the one is in your system located in /usr/bin/python
Before we make the changes, the default version of python in my system was python 2.7.17.
python --version
Python 2.7.17
To make python3 as default python by replacing python2 in Ubuntu.
Open Terminal
cd
nano ~/.bashrc
alias python=python3 (Add this line on top of .bashrc file)
Press ctr+o (To save the file)
Press Enter
Press ctr+x (To exit the file)
source ~/.bashrc OR . ~/.bashrc (To refresh the bashrc file)
python --version
Python 3.7.5
Changing the default python version system wide can break some applications that depend on python2. The alternative solution would be to create an alias.
If you are using zsh (the default on Mac OS) run the following from terminal:
echo 'alias python="python3"' >> ~/.zshrc
echo 'alias pip="pip3"' >> ~/.zshrc
According to this S.O. post, changing the default Python interpreter could possibly break some applications that depend on Python 2.
The post also refers to using aliasing as a solution, and this link might also be a good reference on how to do that.
Personally, I just type "Python3" before I run scripts or go into a shell environment instead of "python".
I have 3 versions of python installed on my Mac. 2 of them are through brew i.e. python2 and python3 while the native version is python. the problem is when I put brew install python it installs python2 and not python. (By saying python means the version which runs on putting that command in terminal). What should I do so that if I type python my brew installed python launches.I have my path variables set correctly and the brew installation path is ahead than that of the usr/bin The problem I am encountering is that I have nltk installed through pip, pip2 and pip3 and when I import nltk in python2 and python3 there is no problem but when I do that in python it show no module found.
Try which python in a terminal to see which python will run. Then you know and can act accordingly to fix it.
ls -lsa $(which python) will let you see if it is a symlink to another location or a real executable. if a Symlink you can see where it points to and so you can follow the breadcrumbs to the final binary used.
if you run python from a terminal and in the python REPL do the following
import sys
print sys.path
you can see to which site-packages locations are pointed.
Other than that you of course have the option to use virtual environments to set up your version of python
if you really want python2 to be the default python command you can add a symlink to your ~/bin folder (create it if it does not exist)
mkdir ~/bin
cd ~/bin
ln -s $(which python2) python
chmod +x python
and make sure that export PATH=~/bin:$PATH is added at the back of your .bashrc or .profile or .zshrc file
Now start a new terminal session and try out python again it should point to brews version
Hope that helps
I installed anaconda and now I can't use pip to install packages on my version 3.6 of python, instead it installs them on anaconda. If I type pip -V I get:
pip 9.0.1 from /anaconda/lib/python3.6/site-packages (python 3.6)
so how do I make it so that it shows:
/Library/Frameworks/Python.framework/Versions/3.6/
instead?.
Or am I missing something?
Well, anaconda comes with its own python directory, which replaces your default python and thus renders its pip useless.
You need to edit .bashrc (or .zshrc in case you are using zsh). There you need to change the path to your original python directory. First of all delete anaconda related export PATH and put in:
export PATH="/Library/Frameworks/Python.framework/Versions/3.6/bin:$PATH"
If you are using Debian based system. You can also try update-alternatives. This is very powerful (yet easy to use) tool, which allows you to change current default python version without manually updating .bashrc.
How to use update-alternatives can be found here: https://linuxconfig.org/how-to-change-from-default-to-alternative-python-version-on-debian-linux#h2-change-python-version-system-wide
I had to work this out myself awhile back:
On Windows 10, I entered command prompt (iecmd) and used:
python -m pip install --target=C:\Users\myusername\AppData\Local\Programs\Python\Python36-32\
modulename
I assume if you can find the folder your python 3.6 then you'll be able to use:
python -m pop install --target=whereever\your\python\is themoduleyouwant
Note that the space between the path and the module name is necessary.
On my Fedora11 machine which has python2.6 pre-installed on it, I was able to successfully install python 2.7 using the following steps:
wget http://www.python.org/ftp/python/2.7/Python-2.7.tar.bz2
tar -xvjf Python-2.7.tar.bz2
cd Python*
./configure --prefix=/opt/python27
make
make install
vi ~/.bash_profile
## replaced PATH=$PATH:$HOME/bin
## with PATH=$PATH:$HOME/bin:/opt/python27/bin
## reload .bash_profile
source ~/.bash_profile
echo "/opt/python27/lib" > /etc/ld.so.conf.d/python27.conf
ldconfig
However, when I checked the python version the system uses via terminal (python -V), it still shows python 2.6.
How will I make the system use python2.7 as its default python?
Or if possible, how will I uninstall python2.6?
Thanks in advance!
Uninstalling the system Python is a bad idea. There are many other packages and softwares that depend on it. It'll be better that you use python2.7 by either modifying the $PATH or creating an alias e.g. python2.7 that points to the python that you installed in /opt dir.
Uninstalling fedora-provided python 2.6 might break many packages that depend on it. I advise you against doing it.
Now, your problem is simply that $PATH and similar variables ($MAN_PATH etc.) are searched from left to right. You appended your new /opt/python27/bin after standard locations like /usr/bin. Reverse the order, and you will get /opt/python27/bin/python as a default python binary.
First of all - never ever try to uninstall Python on RHEL/CentOS/Fedora. yum is written in Python and there will be many problems with repairing the system.
If you want the system to use Python2.7 by default, find where the Python2.6 (use whereis python or which python commands) binary is located, backup it and replace with the binary of Python2.7
Instead of uninstall older version, use specific version of python while using it
I changed symbolic link
ln -s /usr/local/bin/python2.7 /usr/local/bin/python
And used
python -m pip install pip --upgrade
Or you can simply use Yum feature of linux & run command yum remove python it will delete python & related dependencies from the system