The module in Example 15-7 implements general tools for wrapping long lines, at either a fixed column or the first delimiter at or before a fixed column. PyMailGUI uses this file’s wrapText1 function for text in view, reply, and forward windows, but this code is potentially useful in other programs. Run the file as a script to watch its self-test code at work, and study its functions to see its text-processing logic.

Example 15-7. PP3E\Internet\Email\PyMailGui\wraplines.py

################################################################ # split lines on fixed columns or at delimiters before a column
# see also: related but different textwrap standard library module (2.3+) ###############################################################

defaultsize = 80

def wrapLinesSimple(lineslist, size=defaultsize):
    "split at fixed position size"
    wraplines = []
    for line in lineslist:
        while True:
        wraplines.append(line[:size])   # OK if len < size
        line = line[size:]              # split without analysis
        if not line: break
    return wraplines

def wrapLinesSmart(lineslist, size=defaultsize, delimiters='.,:\t '):
    "wrap at first delimiter left of size" 
    wraplines = []
    for line in lineslist:
        while True:
            if len(line) <= size:
                wraplines += [line]
                break
            else:
                for look in range(size-1, size/2, -1):
                    if line[look] in delimiters:
                        front, line = line[:look+1], line[look+1:]
                        break
                else:
                    front, line = line[:size], line[size:]
                wraplines += [front]
    return wraplines

################################################################ # common use case utilities ###############################################################

def wrapText1(text,
size=defaultsize):                  # better for line-based txt: mail
    "when text read all at once"    # keeps original line brks struct
    lines = text.split('\n')        # split on newlines

lines = wrapLinesSmart(lines, size)	# wrap lines on delimiters
return '\n'.join(lines)	# put back together
def wrapText2(text, size=defaultsize):	# more uniform across lines
"same, but treat as one long line"	# but loses original line struct
text = text.replace('\n', ' ')	# drop newlines if any
lines = wrapLinesSmart([text], size)	# wrap single line on delimiters
return lines	# caller puts back together
def wrapText3(text, size=defaultsize):
"same, but put back together"
lines = wrapText2(text, size)	# wrap as single long line
return '\n'.join(lines) + '\n'	# make one string with newlines
def wrapLines1(lines, size=defaultsize):
"when newline included at end"
lines = [line[:-1] for line in lines]	# strip off newlines (or .rstrip)
lines = wrapLinesSmart(lines, size)	# wrap on delimiters
return [(line + '\n') for line in lines]	# put them back
def wrapLines2(lines, size=defaultsize):	# more uniform across lines
"same, but concat as one long line"	# but loses original structure
text = ''.join(lines)	# put together as 1 line
lines = wrapText2(text)	# wrap on delimiters
return [(line + '\n') for line in lines]	# put newlines on ends

################################################################ a self-test ###############################################################

if __name__ == '__main__':
    lines = ['spam ham ' * 20 + 'spam,ni' * 20,
             'spam ham ' * 20,
             'spam,ni'   * 20,
             'spam ham.ni' * 20,
             '',
             'spam'*80,
             ' ',
             'spam ham eggs']
    print 'all', '-'*30
    for line in lines: print repr(line) 
    print 'simple', '-'*30
    for line in wrapLinesSimple(lines): print repr(line)
    print 'smart', '-'*30
    for line in wrapLinesSmart(lines): print repr(line)

    print 'single1', '-'*30
    for line in wrapLinesSimple([lines[0]], 60): print repr(line)
    print 'single2', '-'*30
    for line in wrapLinesSmart([lines[0]], 60): print repr(line)
    print 'combined text', '-'*30
    for line in wrapLines2(lines): print repr(line)
    print 'combined lines', '-'*30
    print wrapText1('\n'.join(lines))

    assert ''.join(lines) == ''.join(wrapLinesSimple(lines, 60))
    assert ''.join(lines) == ''.join(wrapLinesSmart(lines, 60))
    print len(''.join(lines)),
    print len(''.join(wrapLinesSimple(lines))),
    print len(''.join(wrapLinesSmart(lines))),
    print len(''.join(wrapLinesSmart(lines, 60))),
    raw_input('Press enter')