A media type (also known as a Multipurpose Internet Mail Extensions or MIME type) is a standard that indicates the nature and format of a document, file, or assortment of bytes. It is defined and standardized in IETF’s RFC 6838.
Python has a module called mimetypes that you can use to guess the mime type of a file. However, it is not a reliable way to know the mime type of a file. For example,
>>> import mimetypes
>>> print(mimetypes.MimeTypes().guess_type('my_file.txt')[0])
text/plain
You can also use a non-standard module called python-magic to deduce the mimetype of a file. For example,
>>> import magic
>>> mime = magic.Magic(mime=True)
>>> mime.from_file("my_file.txt")
text/plain
See how to detect mime type of a file in Java using Apache Tika library.