Edit File: formatter.py
"""Generic output formatting. Formatter objects transform an abstract flow of formatting events into specific output events on writer objects. Formatters manage several stack structures to allow various properties of a writer object to be changed and restored; writers need not be able to handle relative changes nor any sort of ``change back'' operation. Specific writer properties which may be controlled via formatter objects are horizontal alignment, font, and left margin indentations. A mechanism is provided which supports providing arbitrary, non-exclusive style settings to a writer as well. Additional interfaces facilitate formatting events which are not reversible, such as paragraph separation. Writer objects encapsulate device interfaces. Abstract devices, such as file formats, are supported as well as physical devices. The provided implementations all work with abstract devices. The interface makes available mechanisms for setting the properties which formatter objects manage and inserting data into the output. """ import sys AS_IS = None class NullFormatter: """A formatter which does nothing. If the writer parameter is omitted, a NullWriter instance is created. No methods of the writer are called by NullFormatter instances. Implementations should inherit from this class if implementing a writer interface but don't need to inherit any implementation. """ def __init__(self, writer=None): if writer is None: writer = NullWriter() self.writer = writer def end_paragraph(self, blankline): pass def add_line_break(self): pass def add_hor_rule(self, *args, **kw): pass def add_label_data(self, format, counter, blankline=None): pass def add_flowing_data(self, data): pass def add_literal_data(self, data): pass def flush_softspace(self): pass def push_alignment(self, align): pass def pop_alignment(self): pass def push_font(self, x): pass def pop_font(self): pass def push_margin(self, margin): pass def pop_margin(self): pass def set_spacing(self, spacing): pass def push_style(self, *styles): pass def pop_style(self, n=1): pass def assert_line_data(self, flag=1): pass class AbstractFormatter: """The standard formatter. This implementation has demonstrated wide applicability to many writers, and may be used directly in most circumstances. It has been used to implement a full-featured World Wide Web browser. """ # Space handling policy: blank spaces at the boundary between elements # are handled by the outermost context. "Literal" data is not checked # to determine context, so spaces in literal data are handled directly # in all circumstances. def __init__(self, writer): self.writer = writer # Output device self.align = None # Current alignment self.align_stack = [] # Alignment stack self.font_stack = [] # Font state self.margin_stack = [] # Margin state self.spacing = None # Vertical spacing state self.style_stack = [] # Other state, e.g. color self.nospace = 1 # Should leading space be suppressed self.softspace = 0 # Should a space be inserted self.para_end = 1 # Just ended a paragraph self.parskip = 0 # Skipped space between paragraphs? self.hard_break = 1 # Have a hard break self.have_label = 0 def end_paragraph(self, blankline): if not self.hard_break: self.writer.send_line_break() self.have_label = 0 if self.parskip < blankline and not self.have_label: self.writer.send_paragraph(blankline - self.parskip) self.parskip = blankline self.have_label = 0 self.hard_break = self.nospace = self.para_end = 1 self.softspace = 0 def add_line_break(self): if not (self.hard_break or self.para_end): self.writer.send_line_break() self.have_label = self.parskip = 0 self.hard_break = self.nospace = 1 self.softspace = 0 def add_hor_rule(self, *args, **kw): if not self.hard_break: self.writer.send_line_break() self.writer.send_hor_rule(*args, **kw) self.hard_break = self.nospace = 1 self.have_label = self.para_end = self.softspace = self.parskip = 0 def add_label_data(self, format, counter, blankline = None): if self.have_label or not self.hard_break: self.writer.send_line_break() if not self.para_end: self.writer.send_paragraph((blankline and 1) or 0) if isinstance(format, str): self.writer.send_label_data(self.format_counter(format, counter)) else: self.writer.send_label_data(format) self.nospace = self.have_label = self.hard_break = self.para_end = 1 self.softspace = self.parskip = 0 def format_counter(self, format, counter): label = '' for c in format: if c == '1': label = label + ('%d' % counter) elif c in 'aA': if counter > 0: label = label + self.format_letter(c, counter) elif c in 'iI': if counter > 0: label = label + self.format_roman(c, counter) else: label = label + c return label def format_letter(self, case, counter): label = '' while counter > 0: counter, x = divmod(counter-1, 26) # This makes a strong assumption that lowercase letters # and uppercase letters form two contiguous blocks, with # letters in order! s = chr(ord(case) + x) label = s + label return label def format_roman(self, case, counter): ones = ['i', 'x', 'c', 'm'] fives = ['v', 'l', 'd'] label, index = '', 0 # This will die of IndexError when counter is too big while counter > 0: counter, x = divmod(counter, 10) if x == 9: label = ones[index] + ones[index+1] + label elif x == 4: label = ones[index] + fives[index] + label else: if x >= 5: s = fives[index] x = x-5 else: s = '' s = s + ones[index]*x label = s + label index = index + 1 if case == 'I': return label.upper() return label def add_flowing_data(self, data): if not data: return prespace = data[:1].isspace() postspace = data[-1:].isspace() data = " ".join(data.split()) if self.nospace and not data: return elif prespace or self.softspace: if not data: if not self.nospace: self.softspace = 1 self.parskip = 0 return if not self.nospace: data = ' ' + data self.hard_break = self.nospace = self.para_end = \ self.parskip = self.have_label = 0 self.softspace = postspace self.writer.send_flowing_data(data) def add_literal_data(self, data): if not data: return if self.softspace: self.writer.send_flowing_data(" ") self.hard_break = data[-1:] == '\n' self.nospace = self.para_end = self.softspace = \ self.parskip = self.have_label = 0 self.writer.send_literal_data(data) def flush_softspace(self): if self.softspace: self.hard_break = self.para_end = self.parskip = \ self.have_label = self.softspace = 0 self.nospace = 1 self.writer.send_flowing_data(' ') def push_alignment(self, align): if align and align != self.align: self.writer.new_alignment(align) self.align = align self.align_stack.append(align) else: self.align_stack.append(self.align) def pop_alignment(self): if self.align_stack: del self.align_stack[-1] if self.align_stack: self.align = align = self.align_stack[-1] self.writer.new_alignment(align) else: self.align = None self.writer.new_alignment(None) def push_font(self, font): size, i, b, tt = font if self.softspace: self.hard_break = self.para_end = self.softspace = 0 self.nospace = 1 self.writer.send_flowing_data(' ') if self.font_stack: csize, ci, cb, ctt = self.font_stack[-1] if size is AS_IS: size = csize if i is AS_IS: i = ci if b is AS_IS: b = cb if tt is AS_IS: tt = ctt font = (size, i, b, tt) self.font_stack.append(font) self.writer.new_font(font) def pop_font(self): if self.font_stack: del self.font_stack[-1] if self.font_stack: font = self.font_stack[-1] else: font = None self.writer.new_font(font) def push_margin(self, margin): self.margin_stack.append(margin) fstack = filter(None, self.margin_stack) if not margin and fstack: margin = fstack[-1] self.writer.new_margin(margin, len(fstack)) def pop_margin(self): if self.margin_stack: del self.margin_stack[-1] fstack = filter(None, self.margin_stack) if fstack: margin = fstack[-1] else: margin = None self.writer.new_margin(margin, len(fstack)) def set_spacing(self, spacing): self.spacing = spacing self.writer.new_spacing(spacing) def push_style(self, *styles): if self.softspace: self.hard_break = self.para_end = self.softspace = 0 self.nospace = 1 self.writer.send_flowing_data(' ') for style in styles: self.style_stack.append(style) self.writer.new_styles(tuple(self.style_stack)) def pop_style(self, n=1): del self.style_stack[-n:] self.writer.new_styles(tuple(self.style_stack)) def assert_line_data(self, flag=1): self.nospace = self.hard_break = not flag self.para_end = self.parskip = self.have_label = 0 class NullWriter: """Minimal writer interface to use in testing & inheritance. A writer which only provides the interface definition; no actions are taken on any methods. This should be the base class for all writers which do not need to inherit any implementation methods. """ def __init__(self): pass def flush(self): pass def new_alignment(self, align): pass def new_font(self, font): pass def new_margin(self, margin, level): pass def new_spacing(self, spacing): pass def new_styles(self, styles): pass def send_paragraph(self, blankline): pass def send_line_break(self): pass def send_hor_rule(self, *args, **kw): pass def send_label_data(self, data): pass def send_flowing_data(self, data): pass def send_literal_data(self, data): pass class AbstractWriter(NullWriter): """A writer which can be used in debugging formatters, but not much else. Each method simply announces itself by printing its name and arguments on standard output. """ def new_alignment(self, align): print "new_alignment(%r)" % (align,) def new_font(self, font): print "new_font(%r)" % (font,) def new_margin(self, margin, level): print "new_margin(%r, %d)" % (margin, level) def new_spacing(self, spacing): print "new_spacing(%r)" % (spacing,) def new_styles(self, styles): print "new_styles(%r)" % (styles,) def send_paragraph(self, blankline): print "send_paragraph(%r)" % (blankline,) def send_line_break(self): print "send_line_break()" def send_hor_rule(self, *args, **kw): print "send_hor_rule()" def send_label_data(self, data): print "send_label_data(%r)" % (data,) def send_flowing_data(self, data): print "send_flowing_data(%r)" % (data,) def send_literal_data(self, data): print "send_literal_data(%r)" % (data,) class DumbWriter(NullWriter): """Simple writer class which writes output on the file object passed in as the file parameter or, if file is omitted, on standard output. The output is simply word-wrapped to the number of columns specified by the maxcol parameter. This class is suitable for reflowing a sequence of paragraphs. """ def __init__(self, file=None, maxcol=72): self.file = file or sys.stdout self.maxcol = maxcol NullWriter.__init__(self) self.reset() def reset(self): self.col = 0 self.atbreak = 0 def send_paragraph(self, blankline): self.file.write('\n'*blankline) self.col = 0 self.atbreak = 0 def send_line_break(self): self.file.write('\n') self.col = 0 self.atbreak = 0 def send_hor_rule(self, *args, **kw): self.file.write('\n') self.file.write('-'*self.maxcol) self.file.write('\n') self.col = 0 self.atbreak = 0 def send_literal_data(self, data): self.file.write(data) i = data.rfind('\n') if i >= 0: self.col = 0 data = data[i+1:] data = data.expandtabs() self.col = self.col + len(data) self.atbreak = 0 def send_flowing_data(self, data): if not data: return atbreak = self.atbreak or data[0].isspace() col = self.col maxcol = self.maxcol write = self.file.write for word in data.split(): if atbreak: if col + len(word) >= maxcol: write('\n') col = 0 else: write(' ') col = col + 1 write(word) col = col + len(word) atbreak = 1 self.col = col self.atbreak = data[-1].isspace() def test(file = None): w = DumbWriter() f = AbstractFormatter(w) if file is not None: fp = open(file) elif sys.argv[1:]: fp = open(sys.argv[1]) else: fp = sys.stdin for line in fp: if line == '\n': f.end_paragraph(1) else: f.add_flowing_data(line) f.end_paragraph(0) if __name__ == '__main__': test()