用书上的例子实现在解析HTML文本时，对"<>"中的符号不进行字符转换。
import sys
import string
from optparse import OptionParser
CHAR_MAP = dict(zip(
string.ascii_lowercase,
string.ascii_lowercase[13:26] + string.ascii_lowercase[0:13]
)
)
class RotateStream(object):
"""
General purpost ROT13 Translator
A ROT13 translator smart enough to skip
Markup tags if that's what we want.
"""
MARKUP_START = '<'
MARKUP_END = '>'
def __init__(self, skip_tags):
self.skip_tags = skip_tags
def rotate13_letter(self, letter):
"""
Return the 13-char rotation of a letter.
"""
do_upper = False
if letter.isupper():
do_upper = True
letter = letter.lower()
if letter not in CHAR_MAP:
return letter
else:
letter = CHAR_MAP[letter]
if do_upper:
letter = letter.upper()
return letter
def rotate_from_file(self,handle):
"""
Rotate from a file handle.
Take a file-like object and translates
text file it into ROT13
"""
state_markup = False
for line in handle:
for char in line:
if self.skip_tags:
if state_markup:
#here we're looking for a closing '>'
if char == self.MARKUP_END:
state_markup = False
#char = char
else:
#Not in a markup state, rotate
#unless we're starting a new tag
if char == self.MARKUP_START:
state_markup = True
else:
char = self.rotate13_letter(char)
else:
char = self.rotate13_letter(char)
#Make this a generator
yield char
if __name__ == '__main__':
parser = OptionParser()
parser.add_option('-t', '--tags', dest = "tags",
help = "Ignore Markup Tags", default = False,
action = "store_true")
options, args = parser.parse_args()
print("options tags is ", options.tags)
rot = RotateStream(options.tags)
for letter in rot.rotate_from_file(sys.stdin):
sys.stdout.write(letter)
