email.parser
: Parsing email messagesSource code: Lib/email/parser.py
[UNKNOWN NODE transition]Message object structures can be created in one of two ways: they can be
created from whole cloth by creating an EmailMessage
object, adding headers using the dictionary interface, and adding payload(s)
using set_content()
and related methods, or
they can be created by parsing a serialized representation of the email
message.
The email
package provides a standard parser that understands most email
document structures, including MIME documents. You can pass the parser a
bytes, string or file object, and the parser will return to you the root
EmailMessage
instance of the object structure. For
simple, non-MIME messages the payload of this root object will likely be a
string containing the text of the message. For MIME messages, the root object
will return True
from its is_multipart()
method, and the subparts can be accessed via the payload manipulation methods,
such as get_body()
,
iter_parts()
, and
walk()
.
There are actually two parser interfaces available for use, the Parser
API and the incremental FeedParser
API. The Parser
API is
most useful if you have the entire text of the message in memory, or if the
entire message lives in a file on the file system. FeedParser
is more
appropriate when you are reading the message from a stream which might block
waiting for more input (such as reading an email message from a socket). The
FeedParser
can consume and parse the message incrementally, and only
returns the root object when you close the parser.
Note that the parser can be extended in limited ways, and of course you can
implement your own parser completely from scratch. All of the logic that
connects the email
package's bundled parser and the
EmailMessage
class is embodied in the policy
class, so a custom parser can create message object trees any way it finds
necessary by implementing custom versions of the appropriate policy
methods.
The BytesFeedParser
, imported from the email.feedparser
module,
provides an API that is conducive to incremental parsing of email messages,
such as would be necessary when reading the text of an email message from a
source that can block (such as a socket). The BytesFeedParser
can of
course be used to parse an email message fully contained in a bytes-like
object, string, or file, but the BytesParser
API may be more
convenient for such use cases. The semantics and results of the two parser
APIs are identical.
The BytesFeedParser
's API is simple; you create an instance, feed it a
bunch of bytes until there's no more to feed it, then close the parser to
retrieve the root message object. The BytesFeedParser
is extremely
accurate when parsing standards-compliant messages, and it does a very good job
of parsing non-compliant messages, providing information about how a message
was deemed broken. It will populate a message object's
defects
attribute with a list of any
problems it found in a message. See the email.errors
module for the
list of defects that it can find.
Here is the API for the BytesFeedParser
:
class email.parser.BytesFeedParser(_factory=None, *, policy=policy.compat32)
Create a BytesFeedParser
instance. Optional _factory is a
no-argument callable; if not specified use the
message_factory
from the policy. Call
_factory whenever a new message object is needed.
If policy is specified use the rules it specifies to update the
representation of the message. If policy is not set, use the
compat32
policy, which maintains backward
compatibility with the Python 3.2 version of the email package and provides
Message
as the default factory. All other policies
provide EmailMessage
as the default _factory. For
more information on what else policy controls, see the
policy
documentation.
Note: The policy keyword should always be specified; The default will
change to email.policy.default
in a future version of Python.
New in version 3.2.
Changed in version 3.3: Added the policy keyword.
Changed in version 3.6: _factory defaults to the policy message_factory
.
feed(data)
Feed the parser some more data. data should be a bytes-like object containing one or more lines. The lines can be partial and the parser will stitch such partial lines together properly. The lines can have any of the three common line endings: carriage return, newline, or carriage return and newline (they can even be mixed).
close()
Complete the parsing of all previously fed data and return the root
message object. It is undefined what happens if feed()
is called
after this method has been called.
class email.parser.FeedParser(_factory=None, *, policy=policy.compat32)[source]
Works like BytesFeedParser
except that the input to the
feed()
method must be a string. This is of limited
utility, since the only way for such a message to be valid is for it to
contain only ASCII text or, if utf8
is
True
, no binary attachments.
Changed in version 3.3: Added the policy keyword.
The BytesParser
class, imported from the email.parser
module,
provides an API that can be used to parse a message when the complete contents
of the message are available in a bytes-like object or file. The
email.parser
module also provides Parser
for parsing strings,
and header-only parsers, BytesHeaderParser
and
HeaderParser
, which can be used if you're only interested in the
headers of the message. BytesHeaderParser
and HeaderParser
can be much faster in these situations, since they do not attempt to parse the
message body, instead setting the payload to the raw body.
class email.parser.BytesParser(_class=None, *, policy=policy.compat32)
Create a BytesParser
instance. The _class and policy
arguments have the same meaning and semantics as the _factory
and policy arguments of BytesFeedParser
.
Note: The policy keyword should always be specified; The default will
change to email.policy.default
in a future version of Python.
Changed in version 3.3: Removed the strict argument that was deprecated in 2.4. Added the policy keyword.
Changed in version 3.6: _class defaults to the policy message_factory
.
parse(fp, headersonly=False)
Read all the data from the binary file-like object fp, parse the
resulting bytes, and return the message object. fp must support
both the readline()
and the read()
methods.
The bytes contained in fp must be formatted as a block of RFC 5322
(or, if utf8
is True
, RFC 6532)
style headers and header continuation lines, optionally preceded by an
envelope header. The header block is terminated either by the end of the
data or by a blank line. Following the header block is the body of the
message (which may contain MIME-encoded subparts, including subparts
with a Content-Transfer-Encoding
of 8bit
.
Optional headersonly is a flag specifying whether to stop parsing after
reading the headers or not. The default is False
, meaning it parses
the entire contents of the file.
parsebytes(bytes, headersonly=False)
Similar to the parse()
method, except it takes a bytes-like
object instead of a file-like object. Calling this method on a
bytes-like object is equivalent to wrapping bytes in a
BytesIO
instance first and calling parse()
.
Optional headersonly is as with the parse()
method.
New in version 3.2.
class email.parser.BytesHeaderParser(_class=None, *, policy=policy.compat32)
Exactly like BytesParser
, except that headersonly
defaults to True
.
New in version 3.3.
class email.parser.Parser(_class=None, *, policy=policy.compat32)[source]
This class is parallel to BytesParser
, but handles string input.
Changed in version 3.3: Removed the strict argument. Added the policy keyword.
Changed in version 3.6: _class defaults to the policy message_factory
.
parse(fp, headersonly=False)[source]
Read all the data from the text-mode file-like object fp, parse the
resulting text, and return the root message object. fp must support
both the readline()
and the
read()
methods on file-like objects.
Other than the text mode requirement, this method operates like
BytesParser.parse()
.
parsestr(text, headersonly=False)[source]
Similar to the parse()
method, except it takes a string object
instead of a file-like object. Calling this method on a string is
equivalent to wrapping text in a StringIO
instance first
and calling parse()
.
Optional headersonly is as with the parse()
method.
class email.parser.HeaderParser(_class=None, *, policy=policy.compat32)[source]
Exactly like Parser
, except that headersonly
defaults to True
.
Since creating a message object structure from a string or a file object is such
a common task, four functions are provided as a convenience. They are available
in the top-level email
package namespace.
email.message_from_bytes(s, _class=None, *, policy=policy.compat32)
Return a message object structure from a bytes-like object. This is
equivalent to BytesParser().parsebytes(s)
. Optional _class and
strict are interpreted as with the BytesParser
class
constructor.
New in version 3.2.
Changed in version 3.3: Removed the strict argument. Added the policy keyword.
message_from_binary_file(fp, _class=None, *,
policy=policy.compat32)
Return a message object structure tree from an open binary file
object. This is equivalent to BytesParser().parse(fp)
. _class and
policy are interpreted as with the BytesParser
class
constructor.
New in version 3.2.
Changed in version 3.3: Removed the strict argument. Added the policy keyword.
email.message_from_string(s, _class=None, *, policy=policy.compat32)[source]
Return a message object structure from a string. This is equivalent to
Parser().parsestr(s)
. _class and policy are interpreted as
with the Parser
class constructor.
Changed in version 3.3: Removed the strict argument. Added the policy keyword.
email.message_from_file(fp, _class=None, *, policy=policy.compat32)[source]
Return a message object structure tree from an open file object.
This is equivalent to Parser().parse(fp)
. _class and policy are
interpreted as with the Parser
class constructor.
Changed in version 3.3: Removed the strict argument. Added the policy keyword.
Changed in version 3.6: _class defaults to the policy message_factory
.
Here's an example of how you might use message_from_bytes()
at an
interactive Python prompt:
>>> import email
>>> msg = email.message_from_bytes(myBytes)
Here are some notes on the parsing semantics:
- Most non-
multipart
type messages are parsed as a single message object with a string payload. These objects will returnFalse
foris_multipart()
, anditer_parts()
will yield an empty list. - All
multipart
type messages will be parsed as a container message object with a list of sub-message objects for their payload. The outer container message will returnTrue
foris_multipart()
, anditer_parts()
will yield a list of subparts. - Most messages with a content type of
message/*
(such asmessage/delivery-status
andmessage/rfc822
) will also be parsed as container object containing a list payload of length 1. Theiris_multipart()
method will returnTrue
. The single element yielded byiter_parts()
will be a sub-message object. - Some non-standards-compliant messages may not be internally consistent about
their
multipart
-edness. Such messages may have aContent-Type
header of typemultipart
, but theiris_multipart()
method may returnFalse
. If such messages were parsed with theFeedParser
, they will have an instance of theMultipartInvariantViolationDefect
class in their defects attribute list. Seeemail.errors
for details.