#!/usr/bin/env python from pyparsing import * # pyparsing documentation: # https://sourceforge.net/p/pyparsing/code/HEAD/tree/trunk/src/HowToUsePyparsing.txt#l302 STREAM_FIELDS = {"type", "filename", "num"} # see http://stackoverflow.com/questions/11180622/optional-string-segment-in-pyparsing def assign_missing_fields(fields): """Fill in missing optional field values (filename, num).""" not_found = STREAM_FIELDS - set(fields.keys()) for k in not_found: v = 0 if (k in ["num"]) else "" # see http://pyparsing.wikispaces.com/share/view/71042464 fields[k] = v fields.append(v) def parser_bnf(): """Grammar for parsing podcast configuration files.""" at = Literal("@").suppress() caret = Literal("^") colon = Literal(":").suppress() comment_char = Literal("#") hyphen = Literal("-") left_bracket = Literal("[").suppress() period = Literal(".").suppress() right_bracket = Literal("]").suppress() # zero_index ::= [0-9]+ zero_index = Word(nums).setParseAction(lambda s, l, t: int(t[0])) # filename ::= [A-Za-z0-9][-A-Za-z0-9._ ]+ filename_first = Word(alphanums, exact=1) filename_rest = Word(alphanums + "-_. ") filename = Combine(filename_first + Optional(filename_rest)) # millisecs ::= "." [0-9]+ millisecs = (period + (Word(nums).setParseAction( lambda s, l, t: int(t[0][:3].ljust(3, "0"))) .setResultsName("ms"))) # hours, minutes, seconds ::= zero_index hours = zero_index.setResultsName("hh") minutes = zero_index.setResultsName("mm") seconds = zero_index.setResultsName("ss") # timestamp ::= hours ":" minutes ":" seconds [millisecs] timestamp = Group(hours + colon + minutes + colon + seconds + Optional(millisecs)) # duration_file ::= "@", filename # We need a separate item for a lonely duration file timestamp so # that we can attach a parse action just to the lonely case. Using # duration_file alone means the parse action is attached to all # instances of duration_file. duration_file = at + filename lonely_duration_file = at + filename # timespecs ::= timestamp [duration_file | {timestamp}] # If duration_file timestamp is lonely, prepend a zero timestamp. timespecs = Or( [lonely_duration_file.setParseAction( lambda s, l, t: timestamp.parseString("00:00:00.000") + t), timestamp + duration_file, OneOrMore(timestamp)]) # last_frame ::= "-1" | "last" last_frame = oneOf(["-1", "last"]).setParseAction(replaceWith(-1)) # frame_number ::= ":" (zero_index | last_frame) frame_number = colon + Or([zero_index, last_frame]).setResultsName("num") # stream_number ::= ":" zero_index stream_number = colon + zero_index.setResultsName("num") # input_file ::= ":" [filename] input_file = colon + Optional(filename).setResultsName("filename") # previous_segment ::= ":" "^" previous_segment = colon + caret.setResultsName("filename") # frame_input_file ::= input_file | previous_segment frame_input_file = Or([input_file, previous_segment]) # frame_type ::= "frame" | "f" frame_type = oneOf(["f", "frame"]).setParseAction(replaceWith("frame")) # frame_input ::= frame_type [frame_input_file [frame_number]] frame_input = (frame_type.setResultsName("type") + Optional(frame_input_file + Optional(frame_number))) # video_type ::= "video" | "v" video_type = oneOf(["v", "video"]).setParseAction(replaceWith("video")) # video_input ::= video_type [input_file [stream_number]] video_input = (video_type.setResultsName("type") + Optional(input_file + Optional(stream_number))) # audio_type ::= "audio" | "a" audio_type = oneOf(["a", "audio"]).setParseAction(replaceWith("audio")) # audio_input ::= audio_type [input_file [stream_number]] audio_input = (audio_type.setResultsName("type") + Optional(input_file + Optional(stream_number))) # audio_or_video_input ::= audio_input | video_input audio_or_video_input = Or([audio_input, video_input]) # inputspec ::= "[" (audio_or_video_input | frame_input) "]" inputspec = (left_bracket + delimitedList( Or([audio_or_video_input, frame_input]), delim=":") .setParseAction(assign_missing_fields) + right_bracket) # streamspec ::= inputspec [timespecs] streamspec = Group(inputspec + Group(Optional(timespecs)).setResultsName("times")) # config ::= {streamspec} config = ZeroOrMore(streamspec) config.ignore(pythonStyleComment) return config def parse_configuration_file(config_file): """Parse a podcast configuration file.""" parser = parser_bnf() return parser.parseFile(config_file, parseAll=True) def parse_configuration_string(config_string): """Parse a podcast configuration file.""" parser = parser_bnf() return parser.parseString(config_string, parseAll=True) def test_parser(): tests = ["test/config1.txt", "test/config2.txt", "test/config3.txt", "test/config4.txt"] for t in tests: print "==={f}===".format(f=t) r = parse_configuration_file(t) for s in r: print s print " type = {t}".format(t=s["type"]) print " filename = '{f}'".format(f=s["filename"]) print " num = {n}".format(n=s["num"]) print " times = {t}".format(t=s["times"]) for i, t in enumerate(s["times"]): if (isinstance(t, str)): print " punch out after duration of '{f}'".format(f=t) if (isinstance(t, ParseResults)): if (i % 2 == 0): print " punch in at: {hh:02d}:{mm:02d}:{ss:02d}.{ms:03d}".format(hh=t["hh"], mm=t["mm"], ss=t["ss"], ms=t["ms"]) else: print " punch out at: {hh:02d}:{mm:02d}:{ss:02d}.{ms:03d}".format(hh=t["hh"], mm=t["mm"], ss=t["ss"], ms=t["ms"]) print if (__name__ == "__main__"): test_parser()