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i Tried apt install python 3.9 and it reply

Building dependency tree
Reading state information... Done
E: Unable to locate package python3.9
E: Couldn't find any package by glob 'python3.9'
E: Couldn't find any package by regex 'python3.9'
Hansen Gianto
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    You can install Python 3.9 Alpha 5 from the [Deadsnakes PPA](https://launchpad.net/~deadsnakes/+archive/ubuntu/ppa/+index). But be aware: it is an Alpha version. It can and will contain bugs and might be incompatible with many known packages. – Klaus D. Mar 24 '20 at 04:05

2 Answers2

41

If you are on Ubuntu 19.04 eoan (or any other version unsupported by the deadsnakes ppa), you will not be able to install using the deadsnakes ppa.

What you can do instead, is get the source from Python's official website, and install it manually, as described here.

To do so, first, install the dependencies required to build the Python package.

sudo apt install build-essential zlib1g-dev \
libncurses5-dev libgdbm-dev libnss3-dev \
libssl-dev libreadline-dev libffi-dev curl software-properties-common

then download the tarball and extract it:

wget https://www.python.org/ftp/python/3.9.0/Python-3.9.0.tar.xz
tar -xf Python-3.9.0.tar.xz

Then cd to the extracted directory:

cd Python-3.9.0

Now configure the script:

./configure

Now, to install Python3.9 alongside your current Python installation (if any), use:

sudo make altinstall

Lastly, you can verify your installation using

python3.9 --version
Karishma Sukhwani
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Akash Kumar
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16

You are getting that error because you first need to update the package list and the prerequisites. 

sudo apt update
sudo apt install software-properties-common

Then, add the repo ppa:deadsnakes/ppa to your sources list (where you will download python from)

sudo add-apt-repository ppa:deadsnakes/ppa

Make sure to press enter when prompted.

Lastly, install the version of your choice

sudo apt install python3.9

Make sure to read this:

Disclaimer: there's no guarantee of timely updates in case of security problems or other issues. If you want to use them in a security-or-otherwise-critical environment (say, on a production server), you do so at your own risk.

PPA Deadsnake

Will
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