I am on a raspberry pi if that makes a difference. I’d like to install python 3.7 ideally so my projects can work. I’ve googled it and sudo apt-get install python3.7 doesn’t work and I see some other meathods but it involves installing other things and I’m not exactly sure what those things are or do

Sorry for the dumb question. Just installed a fresh Ubuntu 20.4 after a couple of years of not touching Linux. I thought I could just sudo apt-get install python3.7 but that doesn't work.

I'd love to be able to use apt-get to minimize the chances I fuck something up, can I do this without having to download and compile it myself?

More specifically:

When I sudo apt-get install python 3.7 I don't get any errors or anything, I just get the following:

$ sudo apt-get install python3.7
[sudo] password for j: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Note, selecting 'python3.7-2to3' for regex 'python3.7'
Note, selecting 'libpython3.7-stdlib' for regex 'python3.7'
0 upgraded, 0 newly installed, 0 to remove and 9 not upgraded.

Then when I python3.7 I get:

$ python3.7

Command 'python3.7' not found, did you mean:

  command 'python2.7' from deb python2.7 (2.7.18~rc1-2)
  command 'python3.8' from deb python3.8 (3.8.2-1ubuntu1.1)

Try: sudo apt install <deb name>

And if I look in /usr/bin/:

$ ls /usr/bin/ | grep python
python3
python3.8

And:

$ ls -l /usr/bin/python*
lrwxrwxrwx 1 root root       9 júl  8 23:57 /usr/bin/python3 -> python3.8
-rwxr-xr-x 1 root root 5457536 apr 27 15:53 /usr/bin/python3.8

Beginners beware, this post isn't about overwriting the default python installation, but working with alternative installation of other versions of python on your Ubuntu 20. If you overwrite your default python you are likely to encounter several other issues that may cause you to reinstall your OS, so please go through the complete post and try to make alternate installation.

In this post, I am going to write about a way to install specific python version (python 3.7.5) in your Ubuntu 20 system which initially has Python 3.8. Since, the project I have done till now had the Python version of 3.6 and 3.7. But, after I updated my OS to Ubuntu 20, my virtual environment could not be set upped as per the project requirements.

Because I wanted my old projects to be compatible, first, I thought of way to override my python 3.8 with python 3.7 but had so many other issues.

Now, I have found a way to deal with this version issue, which I will be explaining below.

1 Checking, Initial version of Python that comes with Ubuntu 20

$ python3 --version
Python 3.8.2

2 Installation of pip

a. First updating the packages

$ sudo apt update

b. Installation of pip

# The command below will install all the dependencies required for building Python modules.
$ sudo apt install python3-pip

c. Verification of pip installed

$ pip3 --version
pip 20.0.2 from /usr/lib/python3/dist-packages/pip (python 3.8)

3 Install virtualenv in your local system

Virtualenv is where all the packages required for project will be kept without dealing with local system packages.

$ pip3 install virtualenv

If you want to use Python 3.8 in your project, then, below process can be followed.

# my_project is the project directory
$ mkdir my_project && cd my_project

# Create a virtual environment in your project directory
$ python3 -m virtualenv .venv

# Activating the environment
$ source .venv/bin/activate
$ python --version
Python 3.8.2

But, this isn't our objective, we want to use other python version (Lets say Python 3.7.5). So, for that please see the below steps.

First install specific version of python in your local system without causing conflict in local system

# Update and Upgrades of packages
$ sudo apt update  
$ sudo apt upgrade -y

# Next, install the build tools and Python 3.7 dependencies using the following command:
$ sudo apt install build-essential libssl-dev zlib1g-dev libncurses5-dev libncursesw5-dev libreadline-dev libsqlite3-dev libgdbm-dev libdb5.3-dev libbz2-dev libexpat1-dev liblzma-dev tk-dev libffi-dev

# Next, download the source code of Python 3.7 using the wget tool:
$ cd /tmp
$ wget https://www.python.org/ftp/python/3.7.5/Python-3.7.5.tar.xz

# Next, decompress the tar file using:
$ tar xf Python-3.7.5.tar.xz

# Next, navigate inside your decompressed Python-3.7.0 folder:
$ cd Python-3.7.5

# Build Python 3.7.5 code using the configure and make tools:
$ ./configure --enable-optimizations
$ sudo make -j 8

# Next, run the following command to install the Python 3.7.5:
# Prefer "altinstall" than "install" because install will override the current OS python, and will cause other conflicts in OS.
$ sudo make altinstall


# Python 3.7.5 can run using:
$ python3.7 

After the specific version of python is installed successfully.

Create virtual environment in your project with specific version installed

# First know your specific python version installed path
$ which python3.7
/usr/local/bin/python3.7

# my_project is a project directory
$ mkdir my_project && cd my_project

# Create virtualenv with the specific python version path
$ python3 -m virtualenv --python=/usr/local/bin/python3.7 .venv

# Activating the virtualenv 
$ source .venv/bin/activate

# Test the python path and version
$ which python
my_project/.venv/bin/python

# python --version
Python 3.7.5

Now can work on any project as required.

Would like to get recommendation on this process, or any other ways it can be dealt with.