# `email.contentmanager`: Managing MIME Content

Source code: Lib/email/contentmanager.py

New in version 3.6: 1

class email.contentmanager.ContentManager

  Base class for content managers. Provides the standard registry mechanisms to register converters between MIME content and other representations, as well as the `get_content` and `set_content` dispatch methods.

  get_content(msg, *args, **kw)

    Look up a handler function based on the `mimetype` of msg (see next paragraph), call it, passing through all arguments, and return the result of the call. The expectation is that the handler will extract the payload from msg and return an object that encodes information about the extracted data.

    To find the handler, look for the following keys in the registry, stopping with the first one found:

    - the string representing the full MIME type (`maintype/subtype`)

    - the string representing the `maintype`

    - the empty string

    If none of these keys produce a handler, raise a `KeyError` for the full MIME type.

  set_content(msg, obj, *args, **kw)

    If the `maintype` is `multipart`, raise a `TypeError`; otherwise look up a handler function based on the type of obj (see next paragraph), call `clear_content()` on the msg, and call the handler function, passing through all arguments. The expectation is that the handler will transform and store obj into msg, possibly making other changes to msg as well, such as adding various MIME headers to encode information needed to interpret the stored data.

    To find the handler, obtain the type of obj (`typ = type(obj)`), and look for the following keys in the registry, stopping with the first one found:

    - the type itself (`typ`)

    - the type’s fully qualified name (`typ.__module__ + '.' + typ.__qualname__`).

    - the type’s qualname (`typ.__qualname__`)

    - the type’s name (`typ.__name__`).

    If none of the above match, repeat all of the checks above for each of the types in the MRO (`typ.__mro__`). Finally, if no other key yields a handler, check for a handler for the key `None`. If there is no handler for `None`, raise a `KeyError` for the fully qualified name of the type.

    Also add a MIME-Version header if one is not present (see also `MIMEPart`).

  add_get_handler(key, handler)

    Record the function handler as the handler for key. For the possible values of key, see `get_content()`.

  add_set_handler(typekey, handler)

    Record handler as the function to call when an object of a type matching typekey is passed to `set_content()`. For the possible values of typekey, see `set_content()`.

## Content Manager Instances

Currently the email package provides only one concrete content manager, `raw_data_manager`, although more may be added in the future. `raw_data_manager` is the `content_manager` provided by `EmailPolicy` and its derivatives.

email.contentmanager.raw_data_manager

  This content manager provides only a minimum interface beyond that provided by `Message` itself: it deals only with text, raw byte strings, and `Message` objects. Nevertheless, it provides significant advantages compared to the base API: `get_content` on a text part will return a unicode string without the application needing to manually decode it, `set_content` provides a rich set of options for controlling the headers added to a part and controlling the content transfer encoding, and it enables the use of the various `add_` methods, thereby simplifying the creation of multipart messages.

  email.contentmanager.get_content(msg, errors='replace')

    Return the payload of the part as either a string (for `text` parts), an `EmailMessage` object (for `message/rfc822` parts), or a `bytes` object (for all other non-multipart types). Raise a `KeyError` if called on a `multipart`. If the part is a `text` part and errors is specified, use it as the error handler when decoding the payload to unicode. The default error handler is `replace`.

  email.contentmanager.set_content(msg, <'str'>, subtype="plain", charset='utf-8', cte=None, disposition=None, filename=None, cid=None, params=None, headers=None)
  email.contentmanager.set_content(msg, <'bytes'>, maintype, subtype, cte="base64", disposition=None, filename=None, cid=None, params=None, headers=None)
  email.contentmanager.set_content(msg, <'EmailMessage'>, cte=None, disposition=None, filename=None, cid=None, params=None, headers=None)

    Add headers and payload to msg:

    Add a Content-Type header with a `maintype/subtype` value.

    - For `str`, set the MIME `maintype` to `text`, and set the subtype to subtype if it is specified, or `plain` if it is not.

    - For `bytes`, use the specified maintype and subtype, or raise a `TypeError` if they are not specified.

    - For `EmailMessage` objects, set the maintype to `message`, and set the subtype to subtype if it is specified or `rfc822` if it is not. If subtype is `partial`, raise an error (`bytes` objects must be used to construct `message/partial` parts).

    If charset is provided (which is valid only for `str`), encode the string to bytes using the specified character set. The default is `utf-8`. If the specified charset is a known alias for a standard MIME charset name, use the standard charset instead.

    If cte is set, encode the payload using the specified content transfer encoding, and set the Content-Transfer-Encoding header to that value. Possible values for cte are `quoted-printable`, `base64`, `7bit`, `8bit`, and `binary`. If the input cannot be encoded in the specified encoding (for example, specifying a cte of `7bit` for an input that contains non-ASCII values), raise a `ValueError`.

    - For `str` objects, if cte is not set use heuristics to determine the most compact encoding.

    - For `EmailMessage`, per RFC 2046, raise an error if a cte of `quoted-printable` or `base64` is requested for subtype `rfc822`, and for any cte other than `7bit` for subtype `external-body`. For `message/rfc822`, use `8bit` if cte is not specified. For all other values of subtype, use `7bit`.

    Note

    A cte of `binary` does not actually work correctly yet. The `EmailMessage` object as modified by `set_content` is correct, but `BytesGenerator` does not serialize it correctly.

    If disposition is set, use it as the value of the Content-Disposition header. If not specified, and filename is specified, add the header with the value `attachment`. If disposition is not specified and filename is also not specified, do not add the header. The only valid values for disposition are `attachment` and `inline`.

    If filename is specified, use it as the value of the `filename` parameter of the Content-Disposition header.

    If cid is specified, add a Content-ID header with cid as its value.

    If params is specified, iterate its `items` method and use the resulting `(key, value)` pairs to set additional parameters on the Content-Type header.

    If headers is specified and is a list of strings of the form `headername: headervalue` or a list of `header` objects (distinguished from strings by having a `name` attribute), add the headers to msg.

Footnotes

1

  Originally added in 3.4 as a provisional module