A general-purpose package for gaining expression-first capability in Python world. Currently implemented by taking advantage of Python bytecode, and available since Python 3.5, i.e., by using PySExpr as a cross-version compiler, you don't have to worry about the Python version.

See documentation.

All constructors of PySExpr are documented here.

pip install pysexpr

PySExpr is a framework for better(cross-version, efficient, expressiveness) metaprogramming in Python.

PySExpr is not a programming language, but a code generation back end good to be targeted.

PySExpr is a killer tool when it comes to programmable programming in Python. Comparing to using Python ASTs, we have perfect compatibility; in terms of generating Python code, PySExpr directly uses Python bytecode and produces faster code, at the same time you can have block expressions, assignment expressions or multiline-lambdas even in Python 3.5.

As this library is so useful, certainly there're many other scenarios for it to stand out. For example, we can backport Python3.8/PEP572's assignment expressions to Python 3.5+, by composing this library with the mechanisms proposed by future-strings.

from py_sexpr.terms import *
from py_sexpr.stack_vm.emit import module_code

xs = []

main = block(
        assign_star("a", None),
        for_range("a", 1, 10, call(var("print"), var("a"))),
        )
exec(module_code(main), dict(print=xs.append))

assert xs == [1, 2, 3, 4, 5, 6, 7, 8, 9]