pex 2.1.154

---

2.1.154

This release brings three new features:

1. When creating PEXes without specifying an explicit
   --python-shebang, an appropriate shebang is chosen correctly in
   more cases than previously and a warning is emitted when the shebang
   chosen cannot be guaranteed to be correct. The common case this
   helps select the appropriate shebang for is PEXes built using
   --platform or --complete-platform.
2. PEXes can now be created with --no-pre-install-wheels to cut down
   PEX build times with a tradeoff of roughly 10% greater boot overhead
   upon the 1st execution of the PEX file. For PEXes with very large
   dependency sets (machine learning provides common cases), the build
   time savings can be dramatic.
3. PEXes can now be told to install dependencies at runtime on 1st
   execution using parallel processes using --max-install-jobs at PEX
   build time or by setting the PEX_MAX_INSTALL_JOBS environment
   variable at runtime.

The last two features come with complicated tradeoffs and are turned off
by default as a result. If you think they might help some of your use
cases, there is more detail in the command line help for
--no-pre-install-wheels and --max-install-jobs as well as in the
pex --help-variables output for PEX_MAX_INSTALL_JOBS. You can also
find a detailed performance analysis in #2292 for the extreme cases of
very small and very large PEXes. In the end though, experimenting is
probably your best bet.

• Use appropriate shebang for multi-platform PEXes. (#2296)
• Add support for --no-pre-install-wheels and --max-install-jobs. (#2298)