[Python编程(第4版)].(Programming.Python.4th.Edition).Mark.Lutz.文字版

>>> s = b'A\xe4B'

>>> s.decode('latin1')

'AäB'

>>> from email.message import Message

>>> m = Message()

>>> m.set_payload(b'A\xe4B', charset='latin1') # or 'latin-1': see ahead

>>> t = m.as_string()

>>> print(t)

MIME-Version: 1.0

Content-Type: text/plain; charset="latin1"

Content-Transfer-Encoding: base64

QeRC

>>> m.get_content_charset()

'latin1'

Notice how email automatically applies Base64 MIME encoding to non-ASCII text
parts on generation, to conform to email standards. The same is true for the more
specific MIME text subclass of Message:

>>> from email.mime.text import MIMEText

>>> m = MIMEText(b'A\xe4B', _charset='latin1')

>>> t = m.as_string()

>>> print(t)

Content-Type: text/plain; charset="latin1"

MIME-Version: 1.0

Content-Transfer-Encoding: base64

QeRC

>>> m.get_content_charset()

'latin1'

Now, if we parse this message’s text string with email, we get back a new Message whose
text payload is the Base64 MIME-encoded text used to represent the non-ASCII Uni-
code string. Requesting MIME decoding for the payload with decode=1 returns the byte
string we originally attached:

>>> from email.parser import Parser

>>> q = Parser().parsestr(t)

>>> q

<email.message.Message object at 0x019ECA50>

>>> q.get_content_type()

'text/plain'

>>> q._payload

'QeRC\n'

>>> q.get_payload()

'QeRC\n'

>>> q.get_payload(decode=1)

b'A\xe4B'

However, running Unicode decoding on this byte string to convert to text fails if we
attempt to use the platform default on Windows (UTF8). To be more accurate, and

932 | Chapter 13: Client-Side Scripting