smx 0.8.5

Simple python macro expansion

Simple python macro expansion

example:
  - key : %os.environ.get(USER)
  %indent(%include(file_name))
  - other : %iadd(1, 1)
  %indent(%python("
import mod
f = open('myfile.in')
f.read()
output(mod.process(f))
 ")

Allows simple macros to be expanded inline. You can from smx import Smx to evaluate, or evaluate from the command line. Options to import all env vars, or modules from the command line are available. Macros can be nested... so %expand(%include(...)) is a valid syntax.

Used for yml templates, config files, kubernates deployments, simple HTML pages, etc.

Install

pip install smx

Use

   > smx file.in > file.out
   > smx --help

Or from python:

   from smx import Smx
   ctx = Smx()
   ctx.expand("%add(1,1)")
   ctx.expand_io(fin, fout)
   ctx.expand_file(filename, in_place=True)

Including code and files

Macro	Description
indent(str)	each line of the indented string is indented at the level where the indent function was called.
include(str)	include the specified file
strip(str)	strip a string
expand(str)	string is expanded using smx syntax
python(str)	string is expanded using python syntax
module(str)	string is interpreted as a module and imported

Modules

Macro	Description
os....	os functions are included by default, for example os.path.basename(...)
sys....	sys functions are included by default

Misc

Macro	Description
for(name, range, loop)	loop code is expanded for each value in the range
if(val, true-val, false-val)	if val is expanded to non-empty, true-val is executed
add(a, b)	numbers are added
sub(a, b)	numbers are subtracted

Goals

• The syntax should be "macroy" not "pythony" ... that way you can tell, at a glance when there's macros going on... vs python going on.
• Easy to add your own macros by deriving from Smx and adding new functions with the @smx.macro decorator.
• Easy to import python modules and use them in basically any string context
• JSON and YAML template friendly
• Use "as is" in most configuration contexts
• Unsafe by default, but trivial to use "Safe mode" allowing untrusted execution of a strict set of macro expansions

Caveats

Important to remember that all macros result in "strings", so when dealing with macros.