I am using Ubuntu 18.04 in my work computer. I have never used Python2 versions before and it was annoying me to have in my computer because whenever I try to install something related Python I got issue even my default version Python3.6
I could not install pip, I could not install some packages so I wanted to delete Python completely from my computer. However now I can not install any python and getting lots of errors while trying several methods which are shared before on this platform and other websites.
Currently my terminal does not work so I use Xterm.
python --version
bash /usr/lib/command-not-found: /usr/bin/python3: bad interpreter: No such file or directory
whereis python
python: /usr/lib/python2.7 /usr/local/lib/python2.7 /usr/share/python /usr/share/man/man1/python.1.gz
sudo apt install python-minimal
sudo apt --fix-broken install
sudo apt update
I have tried many things I have seen on the web but could not fix. Also I am user in this computer so I do not have root access. Just wanted to know how to fix.
I have installed python 3.7 but still using and showing version of python 2.7 . I want to change it to 3.. I searched it but ı can't did it.
You should not change your syslink python to use python 3 because it is most likely that your system is using that syslink to python 2 for its own tasks and processes, if you change that, you may broke your system.
As Sammy said in a comment, you should use python3 to use that version.
On the pip side, it is probably that your python 3 does not have pip include (it should have it, but I have seen a lot of Python 3 without it). You can check if you have pip doing: python3 -m pip. The -m param is used to execute modules of python installed.
If you do not have pip installed, you can install it following this (which I recommend because always work): https://pip.pypa.io/en/stable/installing/
That is:
Download a script to install pip: curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
Execute the script in order to install pip (with sudo because you're going to modify your system): sudo python3 get-pip.py
Now you should have pip installed and doing python3 -m pip again should show you the help of pip.
If you have pip already installed and no pip3 command in your system, you can always create an alias to python3 -m pip with the name pip3 and problem solved. Also if you don't know or do not want to create alias or executables in the /usr/bin folder, you can always keep using python3 -m pip.
PS: It is highly recommended to use virtualenvs when developing with python. If you do not know what it is, here it is a link to the docs: https://virtualenv.pypa.io/en/latest/
I'm using Ubuntu, how do I instruct pip to use the Python3 installation and not Python2.6? 2.6 is the default installation on Ubuntu. I can't upgrade that as it will break Ubuntu.
Any single pip installation is (roughly) specific to one Python installation. You can, however, have multiple parallel pip installations. Your package manager probably has a package called pip-3.3 or similar. If not, you can manually install it (run the get-pip.py script using Python 3.3), though you'll have to be careful that it ends up in the right place in PATH. You can also use a virtualenv.
Install pip by downloading the source and doing:
python3 setup.py install
Then, you should have a pip3 or a pip-3.3 command that you can use, to instruct pip to install whatever package using python3
Conversely, if you want to migrate to python3 entirely, do which python and follow the symlinks to /usr/local/bin (I think). There, you should be able to sudo ln -s to change what python points to
The scenario is: I am on Ubuntu 11 which comes with Python 2.7, I want to run Mozilla JetPack which supports Python 2.5/2.6 and Google App Engine which only supports Python 2.5.
Read that its not a good idea to remove Python 2.7 as Ubuntu maybe using it. So the correct way is to use virtualenv. But I am quite lost using it. I installed Python 2.5 in /usr/local/python25 following this guide
I tried
jiewmeng#JM:/usr/local/python25/bin$ ./python --version
Python 2.5.5
jiewmeng#JM:/usr/local/python25/bin$ ./python virtualenv /works/tmp/test
./python: can't open file 'virtualenv': [Errno 2] No such file or directory
then the below works but I will be using Python 2.7
jiewmeng#JM:/usr/local/python25/bin$ virtualenv /works/tmp/test
New python executable in /works/tmp/test/bin/python
Installing distribute.................................................................................................................................................................................done.
jiewmeng#JM:/usr/local/python25/bin$ cd /works/tmp/test/bin
jiewmeng#JM:/works/tmp/test/bin$ ls
activate activate_this.py easy_install easy_install-2.7 pip python
jiewmeng#JM:/works/tmp/test/bin$ ./python --version
Python 2.7.1+
Also, how do I then run Mozilla JetPack or Google App Engine with this version of Python? Sorry I am new to Python (and Linux/Ubuntu)
Outline:
First cd to /usr/local/python25/bin
Download setuptools for Python2.5 (setuptools-0.6c11-py2.5.egg)
Install it (sh setuptools-0.6c11-py2.5.egg).
Now install pip (easy_install pip).
Install virtualenv and virtualenvwrapper using pip (pip install v... etc.).
Configure WORKON_HOME for virtualenv wrapper to work (export WORKON_HOME = $HOME/.virtualenvs). You can use any other directory you want (not just $HOME/.virtualenvs). Just make sure to use the full path.
Now create a virtualenv (mkvirtualenv foobar).
Switch to the new virtualenv (workon foobar).
Now install GAE, JetPack and whatever you want using pip install blah
Why did your install not work?
Looks like you did not install virtualenv for Python2.5. Hence this will not work.
jiewmeng#JM:/usr/local/python25/bin$ ./python virtualenv /works/tmp/test
You can check by running ls command in that directory. I suspect you won't find virtualenv file there.
However this worked for you.
jiewmeng#JM:/usr/local/python25/bin$ virtualenv /works/tmp/test
Because it is using the virtualenv file for system default Python2.7. You can check which virtualenv and opening the virtualenv script. You'll see that the #! will point to system default python.
So you need to install the easy_install and pip for Python 2.5 before you can create virtualenv for Python 2.5. Just follow the steps outlined above.
You don't need to do anything fancy outside the virtualenv wrapper. Just use the --python=python2.5 flag (check out the man page for virtualenv form more). It does not matter what version you install it with, you just have to select the right executable for python in the virtual environment.
e.g. mkvirtualenv --python=python2.5 --distribute python25 if the python flag fails, either add a symlink (ln -s) to python25 in your $PATH or use the full path name on the python flag.
Also, default for multiple python installations is to have, for all 'altinstall' versions, a separate python and easy_install. So, for example: python2.5 ,easy_install-2.5 ,python2.6, easy_install-2.6 etc.
Story:
One of the app that i have works on python 2.4 and other on 2.6. I tried to do a sym link of python2.4 to python and things started to break loose on ubuntu jaunty.
Now i am downloading every dependency of 2.4 and installing it using python2.4 setup.py install. The dependencies seem to be endless.
Question1: How will i tell any framework that go and use version so and so pf python like day django to use 2.6 and say mjango to use 2.4? Something like we say use database databasename kinda syntax.
Question2: Is there more elegant way to switch between version as my hack of symlinking was a virtual disaster?
Question3: Can I download a deb for say hardy and make jaunty believe its for her?
Use Virtualenv.
There is more information here: Working with virtualenv.
Using virtualenv you can create a new virtual python environment with whatever version of Python you want for each project or application. You can then activate the appropriate environment when you need it.
To expand on my answer:
You can install multiple versions of Python on your computer (I have 2.4, 2.5, 2.6 and 3.1 on my machine - I install each from source). I use a Mac, and keep my system Python as whatever OS X sets as the default.
I use easy_install to install packages. On ubuntu you can get easy_install like this:
sudo apt-get install python-setuptools
To install virtualenv then do:
easy_install virtualenv
I tend to create a new virtualenv for each project I'm working on and don't give it access to the global site-packages. This keeps all the packages tight together and allows me to have the specific versions of everything I need.
virtualenv -p python2.6 --no-site-packages ~/env/NEW_DJANGO_PROJECT
And then whenever I am doing anything related to this project I activate it:
source ~/env/NEW_DJANGO_PROJECT/bin/activate
If I run python now it uses this new python. If I use easy_install it installs things into my new virtual environment.
So, virtualenv should be able to solve all of your problems.
Pythonbrew is a magical tool. Which can also be called as Python version manager similar to that of RVM-Ruby version manager but Pythonbrew is inspired by Perlbrew.
Pythonbrew is a program to automate the building and installation of Python in the users $HOME.
Dependencies – curl
Before Installing the Pythonbrew, Install “curl” in the machine, to install curl use the below command in the terminal, give the the password for the user when prompted.
$sudo apt-get install curl
After Installing the curl, Now Install Pythonbrew, copy and paste the following commands in the terminal and type the password for the user when prompted.
Recomended method of installation - Easy Install
$ sudo easy_install pythonbrew
To complete the installation, type the following command
$pythonbrew_install
Alternate method of installation:
Use curl command to download the latest version of pythonbrew from github.
curl -kLO http://github.com/utahta/pythonbrew/raw/master/pythonbrew-install
After downloading, change “pythonbrew-install” to “executable”
chmod +x pythonbrew-install
Then, run the pythonbrew-install in the terminal
./pythonbrew-install
Now the Pythonbrew has been installed in the “Home Directory” i.e., /home/user/.pythonbrew
Next, copy and paste the following line to the end of ~/.bashrc
*NOTE: change “user” to your user name in the system
source /home/user/.pythonbrew/etc/bashrc
Thats it! Close the terminal.
Steps to Install different versions of Python:
Open a new terminal, type the following command or copy and paste it.
$pythonbrew install 2.6.6
This will install Python 2.6.6 and to install Python 2.7 or Python 3.2, change the version number in the previous command.
$pythonbrew install 2.7
or
$pythonbrew install 3.2
Update: If you get error while Installing then Install using the below command.
$pythonbrew install --force 2.7
or
$pythonbrew install --force 3.2
How to manage different versions of Python installed in system
For instance, if Python 2.6.6, Python 2.7 and Python 3.2 is installed in your system, switching between the versions can be done as follows:
By default, Python 2.6.6 will be active and in order to switch to Python 2.7 use the below command
$pythonbrew switch 2.7
The default Python is changed to Python 2.7.
Now, to switch to Python 3.2 change the version number in the previous command.
$pythonbrew switch 3.2
Use the below command to check or list the installed Python versions
$pythonbrew list
Use the below command to check or list the available Python Versions to install
$pythonbrew list -k
To uninstall any of the installed Python version (for example to uninstall Python 2.7), use the below command.
$pythonbrew uninstall 2.7
Use the below command to update the Pythonbrew
$pythonbrew update
Use the below command to disable the Pythonbrew and to activate the default version
$pythonbrew off
Enjoy the experience of installing multiple versions of Python in single Linux / ubuntu machine!
I find http://github.com/utahta/pythonbrew much easier to install and use than any other solution.
Just install it and you'll have these options:
pythonbrew install 2.7.2
pythonbrew use 2.7.2 # use 2.7.2 for a current terminal session
pythonbrew switch 2.7.2 # use 2.7.2 by default system wide
pythonbrew uninstall 2.7.2
Note: if you're using a Linux-based operating system with preinstalled Python, switching (system wide) to another version can make things go wrong, so be careful.
A more grassroot approach than Virtualenv is the side-by-side installation of two Python versions.
If there is an existing installation, and you want a second installation into the same root path (e.g. /usr/local), use this target when making install:
make altinstall
When your second installation is Python 2.6, this will leave you with a /usr/local/bin/python2.6 alongside the old /usr/local/bin/python.
A simple way to switch between these two versions is using a shell alias (alias python=/usr/local/bin/python2.6) on the shell where you invoke the interpreter. But this won't work across sub-shells and she-bang invocations.
pyenv is yet another Python manager. The README.md at that link has a good set of instructions, but they basically are:
$ cd
$ git clone git://github.com/yyuu/pyenv.git .pyenv
Then set up your $PATH.
$ echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bash_profile
$ echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile
$ echo 'eval "$(pyenv init -)"' >> ~/.bash_profile
Install the desired versions of Python:
$ pyenv install 2.7.8
After installing you need to run this:
$ pyenv rehash
Then switch to the version of Python you want to run, for the shell:
$ pyenv shell 2.7.8
"Question1: How will i tell any framework that go and use version so and so pf python like day django to use 2.6 and say mjango to use 2.4?"
You simply run them with the specific python version they need. Run mjango with /usr/bin/python2.4 and django with /usr/bin/python2.6. As easy as that.
"Question2: Is there more elegant way to switch between version as my hack of symlinking was a virtual disaster?"
Yes, see above. Have two separate installs of Python, and run explicitly with the different versions.
"Question3: Can I download a deb for say hardy and make jaunty believe its for her?"
That generally works. If it doesn't, it's because it has dependencies that exist in Hardy, and does not exist in Jaunty, and then you can't.
And here is a Question 4 you didn't ask, but should have. ;)
"Is there an easier way to download all those Python modules?"
Yes, there is. Install setuptools, and use easy_install. It will not help you with library dependecies for those Python modules that have C code and need to be compiled. But it will help with all others. easy_install will download and install all the Python dependencies of the module in question in one go. That makes it a lot quicker to install Python modules.
Move to the project directory :
Create an environment :
virtualenv -p python2.7 --no-site-packages ~/env/twoseven
Then activate your source :
source ~/env/twoseven/bin/activate