Yasm is a complete rewrite of the NASM assembler under the "new"
BSD License (some portions are under other licenses, see COPYING
for details). Yasm currently supports the x86 and AMD64 instruction
sets, accepts NASM and GAS assembler syntaxes, outputs binary,
ELF32, ELF64, 32 and 64-bit Mach-O, RDOFF2, COFF, Win32, and
Win64 object formats, and generates source debugging information
in STABS, DWARF 2, and CodeView? 8 formats.

Building of the pythong bindings can be enabled by passing
PYTHON_BINDINGS=yes to the script. This requires Cython,
which is also available from SlackBuilds.org.
