Behavior Quirks

Bad Shebangs in Python Scripts

Various Python scripts under install/bin/ (e.g. pip) have shebangs looking like #!/build/out/python/install/bin/python3. This /build/out/ directory is where the distribution is built from. Python is writing out shebangs for Python scripts with that absolute path.

To work around this issue, you can mass rewrite the shebangs to point the directory where the distribution is extracted/installed to. Here is a sample shell one-liner to get you started:

$ find install/bin/ -type f -exec sed -i '1 s/^#!.*python.*/#!.\/python3/' {} \;

Alternatively, you can sometimes execute python3 -m <module> to get equivalent functionality to what the installed script would do. e.g. to run pip, python3 -m pip ....

Backscape Key Doesn’t work in Python REPL

If you attempt to run python and the backspace key doesn’t erase characters or the arrow keys don’t work as expected, this is because the executable can’t find the terminfo database.

When you type a special key like the backspace key, this is registered as a key press. There is special software (typically readline or libedit) that most interactive programs use that intercepts these special key presses and converts them into special behavior, such as moving the cursor back instead of forward. But because computer environments are different, there needs to be some definition of how these special behaviors are performed. This is the terminfo database.

When readline and libedit are compiled, there is typically a hard-coded set of search locations for the terminfo database baked into the built library. And when you build a program (like Python) locally, you link against readline or libedit and get these default locations for free.

Because python-build-standalone Python distributions compile and use their own version of readline/libedit and because the build environment is different from your machine, the default search locations for the terminfo database built into binaries distributed with this project point to a path that doesn’t exist. The terminfo database cannot be located and readline/libedit do not know how to convert special key presses to special behavior.

The solution to this is to set an environment variable with the location of the terminfo database.

If running a Debian based Linux distribution (including Ubuntu):

$ TERMINFO_DIRS=/etc/terminfo:/lib/terminfo:/usr/share/terminfo

If running a RedHat based Linux distribution:

$ TERMINFO_DIRS=/etc/terminfo:/usr/share/terminfo

If running macOS:

$ TERMINFO_DIRS=/usr/share/terminfo

e.g.:

$ TERMINFO_DIRS=/etc/terminfo:/lib/terminfo:/usr/share/terminfo install/bin/python3.9