Python - delete uuencoding lines

Question

我正在处理许多文本文件，其中（一些）包含uuencoding，可以是.jpg、.pdf或.xlsx的.zip等。我不关心嵌入的uuencoding数据，所以我只想丢弃这些段落，保留其余的文本。我正在努力想出一种方法，只跳过足够的，但不要跳过太多。

总结http://en.wikipedia.org/wiki/Uuencoding每个斑点以开始

begin 644 filename.extension

开头644之后的每一行似乎都以字母开头

M

所以这可能也有帮助。知道如何使用一个函数来删除文件夹（目录）中所有.txt文件的所有行吗？

例如，以下是.jpg uuencoding

GRAPHIC
18
g438975g32h99a01.jpg
begin 644 g438975g32h99a01.jpg
M_]C_X``02D9)1@`!`@$`8`!@``#_[0G64&AO;=&]S:&]P(#,N,``X0DE-`^T`
M`````!``8`````$``0!@`````0`!.$))300-```````$````'CA"24T$&0``
M````!````!XX0DE-`_,```````D```````````$`.$))300*```````!```X
M0DE-)Q````````H``0`````````".$))30/U``````!(`"]F9@`!`&QF9;@`&
M```````!`"]F9@`!`*&9F@`&```````!`#(````!`%H````&```````!`#4`
M```!`"T````&```````!.$))30/X``````!P``#_____________________
M________`^@`````_____________________________P/H`````/______
M______________________#Z`````#_____________________________
M`^@``#A"24T$"```````$`````$```)````"0``````X0DE-!!X```````0`
M````.$))300:``````!M````!@``````````````)P```+`````&`&<`,P`R
M`&@`.0`Y`````0`````````````````````````!``````````````"P````
M)P`````````````````````````````````````````````X0DE-!!$`````
M``$!`#A"24T$%```````!`````(X0DE-!`P`````!SH````!````<````!D`
M``%0```@T```!QX`&``!_]C_X``02D9)1@`!`@$`2`!(``#_[@`.061O8F4`
M9(`````!_]L`A``,"`@("0@,"0D,$0L*"Q$5#PP,#Q48$Q,5$Q,8$0P,#`P,
M#!$,#`P,#`P,#`P,#`P,#`P,#`P,#`P,#`P,#`P,`0T+"PT.#1`.#A`4#@X.
M%!0.#@X.%!$,#`P,#!$1#`P,#`P,$0P,#`P,#`P,#`P,#`P,#`P,#`P,#`P,
M#`P,#`S_P``1"``9`'`#`2(``A$!`Q$!_]T`!``'_!/P```04!`0$!`0$`
M`````````P`!`@0%!@<("0H+`0`!!0$!`0$!`0`````````!``(#!`4&!P@)
M"@L0``$$`0,"!`(%!P8(!0,,,P$``A$#!"$2,05!46$3(G&!,@84D:&Q0B;,D
M%5+!8C,T<H+10P)EK.$P]-U
MX_-&)Y2DA;25Q-3D]*6UQ=7E]59F=H:6IK;&UN;V-T=79W>'EZ>WQ]?G]Q$`
M`@(!`@0$`P0%!@<'!@4U`0`"$0,A,1($05%A<2(3!3*!D12AL4(CP5+1#,D
M8N%R@I)#4Q5C<S3Q)086HK*#!R8UPM)$DU2C%V1%539T9>+RLX3#TW7CT:4
MI(6TE<34Y/2EM<75Y?569G:&EJ;:VQM;F]B

我只想留下

GRAPHIC
18
g438975g32h99a01.jpg

关于背景，请参阅我之前的问题如何从txt文件中删除奇怪的编码

编辑：这是一个尝试

start_marker='begin 644'

with open('fileWithBegin644.txt') as inf:
    ignoreLines = False
    for line in inf:
        if start_marker in line:
            print line,
            ignoreLines = True         
        if not ignoreLines:
    with open("strip_" + inf, "w") as f: 
        f.write(line.get_text().encode('utf-8'))

但我得到以下错误

  File "removeUuencodingFromAll.py", line 10
    with open("strip_" + inf, "w") as f: 
    ^
IndentationError: expected an indented block

Answer 1

我编写了一个相当简单的生成器。因为规范有点乏味（为什么在不同的行上有两个单独的结束标记？），所以它相当庞大，但这里是。它应该同时作为uuencode的验证器，但我只在非常有限的设置中测试过它。

import re
def unuuencode (iterator, collector=None, ignore_length_errors=False):
    """
    Yield lines from iterator except when they are in an uuencode blob.
    If collector is not None, append to it the uuencoded blobs as a list
    of a list of lines, one for each uuencoded blob.
    """
    state = None  # one of { None, 'in_blob', 'closing', 'closed' }
    collectitem = None
    regex = re.compile(r'^begins+[0-7]{3,6}s+.*?(?:r?n)?$')
    for line in iterator:
        if state == None:
            if regex.match(line):
                if collector != None:
                    collectitem = [line]
                state = 'in_blob'
                continue
            else:
                yield line
        else:
            stripped = line.rstrip('rn')
            if state == 'in_blob' and line.startswith('`'):
                state = 'closing'
            if state == 'closing':
                if stripped != '`':
                    raise ValueError('Expected "`" but got "%s"' % line)
                state = 'closed'
            elif state == 'closed':
                if stripped != 'end':
                    raise ValueError('Expected "end" but got "%s"' % line)
                state = None
            else:
                expect = ord(line[0:1])-32
                actual = len(stripped)
                seen = (len(stripped)-1)*6/8
                if seen != expect:
                    if not ignore_length_errors:
                        raise ValueError('Wrong prefix on line: %s '
                            '(indicated %i, 6/8 %i, actual length %i)' % (
                                line, expect, seen, actual))
                if line[0:1] != 'M':
                    state = 'closing'
            if collectitem:
                collectitem.append(line)
            if state is None:
                if collectitem:
                    collector.append(collectitem)
                    collectitem = None
            continue

这样使用：

with open(file, 'r') as f:
    lines = [x for x in unuuencode(f)]

或者像这样：

with open(file, 'r') as f:
    blobs = []
    lines = [x for x in unuuencode(f, collector=blobs)]

或者像这样：

with open(file, 'r') as f:
    lines = f.read().split('n')
# ... or whichever way you obtained your content as an array of lines
lines = [x for x in unuuencode(lines)]

或者在你似乎正在使用的代码的情况下：

for fi in sys.argv[1:]:
    with open(fi) as markup:
        soup = BeautifulSoup(''.join(unuuencode(markup, ignore_length_errors=True)))
    with open("strip_" + fi, "w") as f:
        f.write(soup.get_text().encode('utf-8'))

您链接到的样本在第二个uuencoded blob中有一个无效的长度指示符，所以我添加了一个选项来忽略它。