Python’s email module can read a message from a file or a string, and generate the same kind of inmemory
object tree that we were generating ourselves in the aforementioned listings. To understand the
e-mail’s content, all you have to do is step through its structure.
Show an example atmime_structure.py`:
import sys, email
def printmsg(msg, level = 0):
prefix = "| " * level
prefix2 = prefix + "|"
print prefix + "+ Message Headers:"
for header, value in msg.items():
print prefix2, header + ":", value
if msg.is_multipart():
for item in msg.get_payload():
printmsg(item, level + 1)
msg = email.message_from_file(sys.stdin)
printmsg(msg)
This program is short and simple. For each object it encounters, it checks to see if it is multipart; if
so, the children of that object are displayed as well.
Individual parts of a message can easily be extracted. You will recall that there are several ways that
message data may be encoded; fortunately, the email module can decode them all! mime_decode.pyshows a
program that will let you decode and save any component of a MIME message:
import sys, email
counter = 0
parts = []
def printmsg(msg, level = 0):
global counter
l = "| " * level
if msg.is_multipart():
print l + "Found multipart:"
for item in msg.get_payload():
printmsg(item, level + 1)
else:
disp = ['%d. Decodable part' % (counter + 1)]
if 'content-type' in msg:
disp.append(msg['content-type'])
if 'content-disposition' in msg:
disp.append(msg['content-disposition'])
print l + ", ".join(disp)
counter += 1
parts.append(msg)
inputfd = open(sys.argv[1])
msg = email.message_from_file(inputfd)
printmsg(msg)
while 1:
print "Select part number to decode or q to quit: "
part = sys.stdin.readline().strip()
if part == 'q':
sys.exit(0)
try:
part = int(part)
msg = parts[part - 1]
except:
print "Invalid selection."
continue
print "Select file to write to:"
filename = sys.stdin.readline().strip()
try:
fd = open(filename, 'wb')
except:
print "Invalid filename."
continue
fd.write(msg.get_payload(decode = 1))
This program steps through the message, like the last example. We skip asking the user about message components that are multipart because those exist only to contain other message objects, like text and attachments; multipart sections have no actual payload of their own.