elide-to-card.py

#!/usr/bin/env python

"""
Convert an 'elide' file to a flashy card file.

A subject.elide file has entries of the form:

    answer
        question
        question
        question
        ... any number of questions

    answer
        question
        question
        ... and so on

    ... any number of answer/question entries.

The input file may have blank lines, which will be skipped, as will
standard # comments. The resulting file will have the logical BNF
structure:

    elide-file      := entry*
    entry           := answer + question-list
    question-list   := question*
    question        := '    ' + prompt
    answer, prompt  := string + newline

The card file is described elsewhere, but briefly, it is an iteration
lines of the form

  question + ' | ' + answer

If the reader just yields (question,answer) pairs, formatting the
output would be trivial.

I would like to write process_input() function as defined below. To do
so I need a elide_reader class. It is also defined below.

"""

import re
import sys

def scan(fh): # Standard comment and blank line stripper
    for line in fh:
        if re.match(r'^(\s|#)*$',line):
            continue # skip line if it has only whitespace and #
        if re.match(r'^\s*#',line):
            continue # skip line if its first non-blank is #
        parts = line.rstrip().split('#')
        yield parts[0] + '\n'

class elide_reader(object):
    # Procedures presented in systematic development order.

    @property
    def more_entries(self):
        return self.buf != ''

    @property
    def more_questions(self):
        if self.more_entries:
            return self.buf.startswith('    ')
        return False

    def read(self):
        line = self.buf
        self._read()
        return line

    def _read(self):
        try:
            self.buf = self.fh.next()
        except StopIteration:
            self.buf = ''

    def __init__(self,fh):
        self.fh = fh
        self._read()

def process_input(fo):
    while fo.more_entries:
        answer = fo.read()
        while fo.more_questions:
            question = fo.read()
            yield (question,answer)

def main():
    efile = scan(sys.stdin)
    for q,a in process_input(elide_reader(efile)):
        q = q.strip()
        a = a.strip()
        print '%s | %s' % (q,a)

main()



testdata = """# About Topeka
Topeka is the capitol of Kansas.
    ? is the capitol of Kansas.
    Topeka is the capitol of ?.

The city of Topeka was founded in 1857.  # official charter
    The city of Topeka was founded in ?.

As of the 2000 census, there were 122,377 people living In Topeka.
    As of the ? census, there were 122,377 people living In Topeka.
    As of the 2000 census, there were ? people living In Topeka.
"""

# print testdata


# mea culpa:
# I forgot to import sys
# In main, I forgot to use elide_reader.