I installed Django on my Ubuntu 21.04 Software but when I use:
python manage.py runserver
I get an error massage :
No module named “Django”
But when I use :
python3 manage.py runserve
It works fine but my python —-version is 3.10.1 and python3 —version is 3.9.x
So what is the error and how I can run it with python only not python3
The issue here is that the python and python3 commands are pointing to two different Python installations/environments altogether.
It looks like you installed Django in your Python 3.9.x environment (the one which you access by typing python3).
On the other hand, your Python 3.10.1 environment (which you access by writing python) seems to have no Django installed.
The pip/pip3 commands are sometimes confusing, and may point to a different Python installation than the one you think they do. This depends entirely on how you set up your Python environments in your machine.
In order to access the pip of a specific Python environment, the best way is to run it as a module, e.g.:
python -m pip [...]
This guarantees that the pip you're using is the one associated with the Python environment you're evoking with the python command.
So in order to install Django on your Python 3.10.1 environment, you need to run:
python -m pip install django
If you use PIP3 to install the module, it will only be installed for Python3. If you use PIP to install the module, the system will use the Python version that is listed first in the PATH variable.
You have multiple Python instances on your machine. To avoid such a problems in the future, it is generally advised to use Virtualenv in Python, if you run code on your general-purpose device. (and have multiple Python instances on your machine)
In order to configure Virtualenv that run the following commands:
sudo apt install python3-venv python3-pip
python3 -m venv venv
Then you activate virtual environment:
source venv/bin/activate
Once the virtual environment is activated, you can install Python modules in this specific virtual environment, this way you will not have to mess up with issues such as the one you have described:
pip install django
and then if you run:
python manage.py runserver,
then it would be running in the context of the specific virtual environment.
I know it is not a direct answer to your problem, but I believe it will help you in avoiding such an issues in the future.
Related
Update update: json_lines is not supported by python versions < 3 - my issue had pretty much nothing to do with environments. I am now using 3.9.1 and all is gucci.
Update: After using which python in my jupyter notebook and in my Terminal, I see that they are both using the same environment. As such I am still at a loss as to why my notebook cannot find json_lines.
I have two python environments on my computer, a default one and one I have for running my jupyter notebook on. I am trying to install the library, json_lines to the latter environment. I am not used the Anaconda environment manager.
On my Mac's Terminal I used the general pip install command pip install json-lines, but when I try to execute the following line of Python import json_lines in my notebook, I still receive the following error ImportError: No module named json_lines.
As I suspect I am not installing to the correct environment, I tried installing the library from inside my notebook with the following, import sys; !{sys.executable} -m pip install jsonlines.
However, this has not changed my dilemma.
Is there some way I can specify from my Terminal which environment to install to? or is it likely I am encountering a different issue to what I suspect?
The package for json_lines in pip in json-lines. Hence you could install it as:
$ pip install json-lines
It may be appropriate to use an isolated python environment for your particular project if you want to use particular conda libraries but without the whole package. In this instance, you would be able to use virtualenv. This will allow you to create an isolated python environment.
$ pip3 install virtualenv
You can call virtualenv to create a virtual python environment with the working name e.g. myvenv.
$ virtualenv myvenv
From here, you can set your terminal to use this python version. If you are on *nix:
$ which python
/usr/bin/python
$ source myvenv/bin/activate
(myvenv)$ which python
/.../myvenv/bin/python
This article can help you out.
https://janakiev.com/blog/jupyter-virtual-envs/
You need to create a virtualenv which will be used by your notebooks.
I recently started using elementary OS. It's based on Ubuntu.
During installation it installs python 3.6.
I installed python 3.8 manually by installing the following packages: python3.8, python3.8-dev, python3.8-minimal, python3.8-venv.
I also updated the link to the python binary with:
sudo ln -sf /usr/bin/python3.8 /usr/bin/python3
After this a couple of things stopped working.
For example when I tried to execute a non-existing command it didn't print the error message that it cannot found the command, but it displayed a python stack trace. That one I solved with:
cd /usr/lib/python3/dist-packages
sudo ln -s apt_pkg.cpython-36m-x86_64-linux-gnu.so apt_pkg.so
sudo ln -s apt_inst.cpython-36m-x86_64-linux-gnu.so apt_inst.so
As you can see the python error was because it couldn't find the compiled binaries for the apt module.
So this issue was solved, but there are a couple of similar ones, and none of them can be solved this way, as the module binary is not compatible with python 3.8.
Is it possible to remove python 3.6 completely and override it with 3.8 so that the module binaries also get updated? Or can python 3.8 and 3.6 coexist? I would be fine with the /usr/bin/python3 link pointing to python 3.6 and I would manually execute /usr/bin/python3.8 or create a different alias or link for it. However when I print out the sys.path with /usr/bin/python3.8 I get this:
/usr/lib/python38.zip
/usr/lib/python3.8
/usr/lib/python3.8/lib-dynload
/home/{username}/.local/lib/python3.8/site-packages
/usr/local/lib/python3.8/dist-packages
/usr/lib/python3/dist-packages
The trouble is with the last one. That's where the modules are with the 3.6 compatible so files. Can I somehow force python 3.8 to completely ignore the last module search path (without always stating sys.path.remove in my scripts) ?
I recommend you undo your symlink overwriting your systemwide version of Python 3. As you have found, replacing the python3 executable might create some problems, as it is used under the hood.
In general, you should leave your system python[3] installation alone for this reason and it is common to use virtual environments. This can be done as follows (assuming you are in some project directory):
python3.8 -m venv venv
source venv/bin/activate
The first command will create a virtual environment ('venv') in the directory venv. The second command will 'activate': now python (and in this case, python3 and python3.8) all refer to your original python3.8 in the context of this shell. You will have to repeat this if you launch a new shell.
This will also allow you to install packages using pip without cluttering your system installation. The use of virtual environments and pip is an incredibly common workflow in the Python development world.
In terms of shell and 'global' Python management, you can also use pyenv to manage your Python versions and what is available in the shell. pyenv is quite nice if you want to run a particular version of python, say 3.8.0 but not 3.8.1.
I am getting started on using Zappa. However, I already had installed python 3.7 on my computer while Zappa uses 3.6. I installed python 3.6.8, but when I try to use zappa in the cmd (zappa init) it uses python 3.7 by default. How can I direct zappa to use 3.6 instead?
As mentioned in Zappa README:
Please note that Zappa must be installed into your project's virtual environment.
You should use something like virtualenv to create a virtual environment, which makes it easy to switch Python version.
If you use virtualenv, you can try create an environment by:
$ virtualenv -p /usr/bin/python3.6 venv
$ source activate venv
Then pip install zappa in this virtual environment.
I don't know about Zappa, but if you want use a specific version of python can do:
python3.6 my_program.py
and if whant use the command python with a specific version permanently, in linux modify the file /home/[user_name]/.bashrc and add the next line:
alias python=python3.6
You can use virtualenv to setup an environment using a specific Python version by:
% pip install virtualenv
% virtualenv -p python3.6 .venv
You can also use an absolute path to the Python executable if it's named the same but located in different folders.
Then switch to use the environment:
% source .venv/bin/activate
This environment uses Python 3.6, so install Zappa with pip like normal and you're good to go.
You can read more about usage of virtualenv here.
I'm running ubuntu 14.04 64-bit.
I created a virtual environment via pythonbrew venv using python 2.7.5.
I created a django application dependent to opentok python-sdk.
When I try to install opentok, it says:
CompressionError: bz2 module is not available.
It works fine using the built in python (/usr/bin/python)
But using the python provided py pythonbrew, I encounter the error.
This is not just another bz2 module error that can be solved by correcting paths as mentioned in a possible duplicate of this question. A pythonbrew virtualenv was used here meaning that this should use a different python other than the system python. The answer there suggests linking to the system python which is not very good. A virtual env is being used here to isolate the system python to the specific python I will use for my project.
First Install bz2 then try installing it again :
sudo apt-get install libbz2-dev
after give your pip command again . Hopefully it will work
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