问题
is there any Python module which helps to decode the various forms of encoded mail headers, mainly Subject, to simple - say - UTF-8 strings?
Here are example Subject headers from mail files that I have:
Subject: [ 201105311136 ]=?UTF-8?B?IMKnIDE2NSBBYnM=?=. 1 AO;
Subject: [ 201105161048 ] GewSt:=?UTF-8?B?IFdlZ2ZhbGwgZGVyIFZvcmzDpHVmaWdrZWl0?=
Subject: [ 201105191633 ]
=?UTF-8?B?IERyZWltb25hdHNmcmlzdCBmw7xyIFZlcnBmbGVndW5nc21laHJhdWZ3ZW5kdW4=?=
=?UTF-8?B?Z2VuIGVpbmVzIFNlZW1hbm5z?=
text - encoded sting - text
text - encoded string
text - encoded string - encoded string
Encodig could also be something else like ISO 8859-15.
Update 1: I forgot to mention, I tried email.header.decode_header
for item in message.items():
if item[0] == 'Subject':
sub = email.header.decode_header(item[1])
logging.debug( 'Subject is %s' % sub )
This outputs
DEBUG:root:Subject is [('[ 201101251025 ] ELStAM;=?UTF-8?B?IFZlcmbDvGd1bmcgdm9tIDIx?=. Januar 2011', None)]
which does not really help.
Update 2: Thanks to Ingmar Hupp in the comments.
the first example decodes to a list of two tupels:
print decode_header("""[ 201105161048 ] GewSt:=?UTF-8?B?IFdlZ2ZhbGwgZGVyIFZvcmzDpHVmaWdrZWl0?=""")
[('[ 201105161048 ] GewSt:', None), (' Wegfall der Vorl\xc3\xa4ufigkeit', 'utf-8')]
is this always [(string, encoding),(string, encoding), ...] so I need a loop to concat all the [0] items to one string or how to get it all in one string?
Subject: [ 201101251025 ] ELStAM;=?UTF-8?B?IFZlcmbDvGd1bmcgdm9tIDIx?=. Januar 2011
does not decode well:
print decode_header("""[ 201101251025 ] ELStAM;=?UTF-8?B?IFZlcmbDvGd1bmcgdm9tIDIx?=. Januar 2011""")
[('[ 201101251025 ] ELStAM;=?UTF-8?B?IFZlcmbDvGd1bmcgdm9tIDIx?=. Januar 2011', None)]
回答1:
This type of encoding is known as MIME encoded-word and the email module can decode it:
from email.header import decode_header
print decode_header("""=?UTF-8?B?IERyZWltb25hdHNmcmlzdCBmw7xyIFZlcnBmbGVndW5nc21laHJhdWZ3ZW5kdW4=?=""")
This outputs a list of tuples, containing the decoded string and the encoding used. This is because the format supports different encodings in a single header. To merge these into a single string you need to convert them into a shared encoding and then concatenate this, which can be accomplished using Python's unicode object:
from email.header import decode_header
dh = decode_header("""[ 201105161048 ] GewSt:=?UTF-8?B?IFdlZ2ZhbGwgZGVyIFZvcmzDpHVmaWdrZWl0?=""")
default_charset = 'ASCII'
print ''.join([ unicode(t[0], t[1] or default_charset) for t in dh ])
Update 2:
The problem with this Subject line not decoding:
Subject: [ 201101251025 ] ELStAM;=?UTF-8?B?IFZlcmbDvGd1bmcgdm9tIDIx?=. Januar 2011
^
Is actually the senders fault, which violates the requirement of encoded-words in a header being separated by white-space, specified in RFC 2047, section 5, paragraph 1: an 'encoded-word' that appears in a header field defined as '*text' MUST be separated from any adjacent 'encoded-word' or 'text' by 'linear-white-space'.
If need be, you can work around this by pre-processing these corrupt headers with a regex that inserts a whitespace after the encoded-word part (unless it's at the end), like so:
import re
header_value = re.sub(r"(=\?.*\?=)(?!$)", r"\1 ", header_value)
回答2:
I was just testing with encoded headers in Python 3.3, and I found that this is a very convenient way to deal with them:
>>> from email.header import Header, decode_header, make_header
>>> subject = '[ 201105161048 ] GewSt:=?UTF-8?B?IFdlZ2ZhbGwgZGVyIFZvcmzDpHVmaWdrZWl0?='
>>> h = make_header(decode_header(subject))
>>> str(h)
'[ 201105161048 ] GewSt: Wegfall der Vorläufigkeit'
As you can see it automatically adds whitespace around the encoded words.
It internally keeps the encoded and ASCII header parts separate as you can see when it re-encodes the non-ASCII parts:
>>> h.encode()
'[ 201105161048 ] GewSt: =?utf-8?q?_Wegfall_der_Vorl=C3=A4ufigkeit?='
If you want the whole header re-encoded you could convert the header to a string and then back into a header:
>>> h2 = Header(str(h))
>>> str(h2)
'[ 201105161048 ] GewSt: Wegfall der Vorläufigkeit'
>>> h2.encode()
'=?utf-8?q?=5B_201105161048_=5D_GewSt=3A__Wegfall_der_Vorl=C3=A4ufigkeit?='
回答3:
def decode_header(value):
return ' '.join((item[0].decode(item[1] or 'utf-8').encode('utf-8') for item in email.header.decode_header(value)))
回答4:
How about decoding headers in the following way:
import poplib, email
from email.header import decode_header, make_header
...
subject, encoding = decode_header(message.get('subject'))[0]
if encoding==None:
print "\n%s (%s)\n"%(subject, encoding)
else:
print "\n%s (%s)\n"%(subject.decode(encoding), encoding)
this gets subject from email and decodes it with specified encoding (or no decoding if encoding set to None).
Worked for me for encodings set as 'None', 'utf-8', 'koi8-r', 'cp1251', 'windows-1251'
回答5:
I had a similar issue, but my case was a little bit different:
- Python 3.5 (The question is from 2011, but still very high on google)
- Read message directly from file as byte-string
Now the cool feature of the python 3 email.parser is that all headers are automatically decoded to Unicode-Strings. However this causes a little "misfortune" when dealing with wrong headers. So following header caused the problem:
Subject: Re: =?ISO-2022-JP?B?GyRCIVYlMyUiMnE1RCFXGyhC?=
(1/9(=?ISO-2022-JP?B?GyRCNmIbKEI=?=) 6:00pm-7:00pm)
=?ISO-2022-JP?B?GyRCJE4kKkNOJGkkOxsoQg==?=
This resulted in the following msg['subject']:
Re: 「コア会議」 (1/9(=?ISO-2022-JP?B?GyRCNmIbKEI=?=) 6:00pm-7:00pm) のお知らせ
Well the issue is uncompliance with RFC 2047 (There should be a line-white-space after the MIME encoded word) as already described in the answer by Ingmar Hupp. So my answer is inspired by his.
Solution 1: Fix byte-string before actually parsing the email. This seemed to be the better solution, however I was struggling to implement a Regex substitution on byte-strings. So I opted for solution 2:
Solution 2: Fix the already parsed and partly-decoded header value:
with open(file, 'rb') as fp: # read as byte-string
msg = email.message_from_binary_file(fp, policy=policy.default)
subject_fixed = fix_wrong_encoded_words_header(msg['subject'])
def fix_wrong_encoded_words_header(header_value):
fixed_header_value = re.sub(r"(=\?.*\?=)(?=\S)", r"\1 ", header_value)
if fixed_header_value == header_value: # nothing needed to fix
return header_value
else:
dh = decode_header(fixed_header_value)
default_charset = 'unicode-escape'
correct_header_value = ''.join([str(t[0], t[1] or default_charset) for t in dh])
return correct_header_value
Explanation of important parts:
I modified the regex of Ingmar Hupp to only replace wrong MIME encoded words: (=\?.*\?=)(?=\S) Debuggex Demo. Because doing for all would heavily slow dow the parsing (Parsing about 150'000 mails).
After applying the decode_header function to the fixed_header, we have following parts in dh:
dh == [(b'Re: \\u300c\\u30b3\\u30a2\\u4f1a\\u8b70\\u300d (1/9(', None),
(b'\x1b$B6b\x1b(B', 'iso-2022-jp'),
(b' ) 6:00pm-7:00pm) \\u306e\\u304a\\u77e5\\u3089\\u305b', None)]
To re-decode the unicode-escaped sequences, we set default_charset = 'unicode-escape' when building the new header-value.
The correct_header_value is now:
Re: 「コア会議」 (1/9(金 ) 6:00pm-7:00pm) のお知らせ'
I hope this will save somebody some time.
Addition: The answer by Sander Steffann didn't really help me, because I wasn't able to get the raw-value of the header-field out of the message-class.
回答6:
This script works fine for me.. I use this script to decode all email subjects
pat2=re.compile(r'(([^=]*)=\?([^\?]*)\?([BbQq])\?([^\?]*)\?=([^=]*))',re.IGNORECASE)
def decodev2(a):
data=pat2.findall(a)
line=[]
if data:
for g in data:
(raw,extra1,encoding,method,string,extra)=g
extra1=extra1.replace('\r','').replace('\n','').strip()
if len(extra1)>0:
line.append(extra1)
if method.lower()=='q':
string=quopri.decodestring(string)
string=string.replace("_"," ").strip()
if method.lower()=='b':
string=base64.b64decode(string)
line.append(string.decode(encoding,errors='ignore'))
extra=extra.replace('\r','').replace('\n','').strip()
if len(extra)>0:
line.append(extra)
return "".join(line)
else:
return a
samples:
=?iso-8859-1?q?una-al-dia_=2806/04/2017=29_Google_soluciona_102_vulnerabi?=
=?iso-8859-1?q?lidades_en_Android?=
=?UTF-8?Q?Al=C3=A9grate?= : =?UTF-8?Q?=20La=20compra=20de=20tu=20vehi?= =?UTF-8?Q?culo=20en=20tan=20s=C3=B3lo=2024h?= =?UTF-8?Q?=2E=2E=2E=20=C2=A1Valoraci=C3=B3n=20=26?= =?UTF-8?Q?ago=20=C2=A0inmediato=21?=
回答7:
Python has an e-mail lib. http://docs.python.org/library/email.header.html
Take a look at email.header.decode_header()
回答8:
for me this worked perfect (and always gives me a string):
dmsgsubject, dmsgsubjectencoding = email.header.decode_header(msg['Subject'])[0]
msgsubject = dmsgsubject.decode(*([dmsgsubjectencoding] if dmsgsubjectencoding else [])) if isinstance(dmsgsubject, bytes) else dmsgsubject
来源：https://stackoverflow.com/questions/7331351/python-email-header-decoding-utf-8