I am building Python 3.10 from source on Ubuntu 18.04, following instructions from several web links, primarily the Python website (https://devguide.python.org/setup) and RealPython (https://realpython.com/installing-python/#how-to-build-python-from-source-code). I extracted Python-3.10.0.tgz into /opt/Python3.10. I have three questions.
First, the Python website says to use ./configure --with-pydebug and RealPython says to use ./configure --enable-optimizations --with-ensurepip=install. Another source says to include --enable-shared and --enable-unicode=ucs4. Which of these is best? Should I use all of those flags?
Second, I currently have Python 3.6 and Python 3.8 installed. They are installed in several directories under /usr. Following the directions I have seen on the web I am building in /opt/Python3.10. I assume that make altinstall (the final build step) will take care of installing the build in the usual folders under /usr, but that's not clear. Should I use ./configure --prefix=directory although none of the web sources mention doing that?
Finally, how much does --enable-optimizations slow down the install process?
This is my first time building Python from source, and it will help to clear these things up. Thanks for any help.
CodePudding user response：
Welcome to the world of Python build configuration! I'll go through the command line options to ./configure one by one.
--with-pydebug is for core Python developers, not developers (like you and me) just using Python. It creates debugging symbols and slows down execution. You don't need it.
--enable-optimizations is good for performance in the long run, at the expense of lengthening the compiling process, possibly by 3-fold (or more), depending on your system. However, it results in faster execution, so I would use it in your situation.
--with-ensurepip=install is good. You want the most up-to-date version of pip.
--enable-shared is maybe not a good idea in your case, so I'd recommend not using it here. Read Difference between static and shared libraries? to understand the difference. Basically, since you'll possibly be installing to a non-system path (/opt/local, see below) that almost certainly isn't on your system's search path for shared libraries, you'll very likely run into problems down the road. A static build has all the pieces in one place, so you can install and run it from wherever. This is at the expense of size - the python binary will be rather large - but is great for non-sys admins. Even if you end up installing to /usr/local, I would argue that static is better/easier than shared.
--enable-unicode=ucs4 is optional, and may not be compatible with your system. You don't need it. ./configure is smart enough to figure out what Unicode settings are best. This option is left over from build instructions that are quite a few versions out of date.
--prefix I would suggest you use --prefix=/opt/local if that directory already exists and is in your $PATH, or if you know how to edit your $PATH in ~/.bashrc. Otherwise, use /usr/local or $HOME. /usr/local is the designated system-wide location for local software installs (i.e., stuff that doesn't come with Ubuntu), and is likely already on your $PATH. $HOME is always an option that doesn't require the use of sudo, which is great from a security perspective. You'll need to add /home/your_username/bin to your $PATH if it isn't already present.