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Hello, I'm Anant Narayan. I'm 10 years old. I want to upgrade the
default Python3 which is Python 3.5.3 to Python 3.7.2. When googled I found many sites telling how to install latest
python 3.5 and other versions including python 3.7.0 but none of these
sites were telling how to upgrade from python 3.5.3 to python 3.7.2
.So I tried to install Python 3.7.2 instead of upgrading the default
Python 3.5.3. After some searches I got a guide on How to install Python 3.7 on Raspberry Pi.Here is the link to the website: https://www.ramoonus.nl/2018/06/30/installing-python-3-7-on-raspberry-pi/ . So I followed the steps and successfully installed Python 3.7.0 on my Raspberry Pi 3 and set the alias of python and python3 to python3.7.0 and now when I enter python --version or python3 --version it gives me 3.7.0. But now I have another problem that is when I shutdown or reboot my Pi and switches it back on and I type python --version it gives me 2.7.13 and python3 it gives me 3.5.3. So please help me with this matter. Thanks in advance.

Great that you are having fun with your PI! I hope I can help you, please leave a comment if you have more questions.

In Linux, an alias is a setting in your shell, the program that you talk with to control your PI. But as soon as you leave your PI, the shell program is closed and the alias setting is thrown away.

To make the change permanent, you can either add the alias setting to the startup file of your shell (the file .profile in your home directory), or better, change the links.

To change .profile, type the following exactly (better to use copy-paste):

echo "alias python3=/usr/local/bin/python3.7" >> ~/.profile

The file .profile is read during login, so to activate the change you must log out and log in again.

In Unix, a link is a file that points to another file. /usr/bin/python normally points to /usr/bin/python2.7, and /usr/bin/python3 points to /usr/bin/python3.5.3. You can see links by adding the -l (l for long) option to ls, for example ls -l /usr/bin/python*. Links have permissions set to lrwxrwxrwx.

I would leave the /usr/bin/python link alone, this is used by the operating system and that expects certain libraries to be installed that are probably not installed in your new python.

If your new python is /usr/local/opt/python-3.7.2/bin/python3.7, you can change the python3 link by typing the following commands:

sudo rm /usr/bin/python3
sudo ln -s /usr/local/bin/python3.7 /usr/bin/python3

 wget https://www.python.org/ftp/python/3.7.2/Python-3.7.2.tgz

 tar xzvf Python-3.7.2.tgz

 cd Python-3.7.2/

 ./configure

 make -j4

 sudo make install

After that simply do:

echo "alias python3=’/usr/local/opt/python-3.7.2/bin/python3.7′" >> ~/.profile

Hope this work