guess_extension()

Return the canonical file extension for a MIME / content type.

Usage

Source

guess_extension(
    content_type,
    with_dot=True,
)

This is the reverse of get_content_type(). The lookup is case-insensitive and any MIME parameters are ignored, so an HTTP Content-Type header value such as text/html; charset=utf-8 resolves the same as text/html. Common non-canonical or legacy spellings are also accepted — text/json resolves like application/json and image/jpg like image/jpeg. When a content type maps to several extensions, the canonical one is returned (e.g. image/jpeg -> .jpg); use guess_all_extensions() to get every extension.

The canonical choice follows this library’s table and may differ from the standard library mimetypes module — for example, this returns .html for text/html.

Parameters

content_type: str

A MIME type to look up, optionally with parameters (e.g. application/pdf or text/html; charset=utf-8).

with_dot: bool = True

When True (default) the returned extension has a leading dot (e.g. .pdf), which is what you concatenate onto a filename. When False the bare extension is returned (e.g. pdf).

Returns

Optional[str]

The canonical extension for the content type, or None if it is unknown

(including empty, whitespace-only, or parameter-only input).

Raises

TypeError

If content_type is None.

Example

>>> guess_extension("application/pdf")
'.pdf'
>>> guess_extension("image/jpeg")
'.jpg'
>>> guess_extension("text/html; charset=utf-8")
'.html'
>>> guess_extension("application/pdf", with_dot=False)
'pdf'
>>> guess_extension("application/x-does-not-exist") is None
True