"Yet Another Python Templating Utility, Version 1.2" import sys # utility stuff to avoid tests in the mainline code class _nevermatch: "Polymorphic with a regex that never matches" def match(self, line): return None _never = _nevermatch() # one reusable instance of it suffices def identity(string, why): "A do-nothing-special-to-the-input, just-return-it function" return string def nohandle(string): "A do-nothing handler that just re-raises the exception" raise # and now the real thing class copier: "Smart-copier (YAPTU) class" def copyblock(self, i=0, last=None): "Main copy method: process lines [i,last) of block" def repl(match, self=self): "return the eval of a found expression, for replacement" # uncomment for debug: print '!!! replacing',match.group(1) expr = self.preproc(match.group(1), 'eval') try: return str(eval(expr, self.globals, self.locals)) except: return str(self.handle(expr)) block = self.locals['_bl'] if last is None: last = len(block) while i Executing: {"+stat+"}" exec stat in self.globals,self.locals i=j+1 else: # normal line, just copy with substitution self.ouf.write(self.regex.sub(repl,line)) i=i+1 def __init__(self, regex=_never, dict={}, restat=_never, restend=_never, recont=_never, preproc=identity, handle=nohandle, ouf=sys.stdout): "Initialize self's attributes" self.regex = regex self.globals = dict self.locals = { '_cb':self.copyblock } self.restat = restat self.restend = restend self.recont = recont self.preproc = preproc self.handle = handle self.ouf = ouf def copy(self, block=None, inf=sys.stdin): "Entry point: copy-with-processing a file, or a block of lines" if block is None: block = inf.readlines() self.locals['_bl'] = block self.copyblock() if __name__=='__main__': "Test: copy a block of lines, with full processing" import re rex=re.compile('@([^@]+)@') rbe=re.compile('\+') ren=re.compile('-') rco=re.compile('= ') x=23 # just a variable to try substitution cop = copier(rex, globals(), rbe, ren, rco) lines_block = [line+'\n' for line in """ A first, plain line -- it just gets copied. A second line, with @x@ substitutions. + x+=1 # non-block statements MUST end with comments - Now the substitutions are @x@. + if x>23: After all, @x@ is rather large! = else: After all, @x@ is rather small! - + for i in range(3): Also, @i@ times @x@ is @i*x@. - One last, plain line at the end.""".split('\n')] print "*** input:" print ''.join(lines_block) print "*** output:" cop.copy(lines_block)