base64 — Base16, Base32, Base64, Base85 Data Encodings

Source code: Lib/base64.py

This module provides functions for encoding binary data to printable ASCII characters and decoding such encodings back to binary data. It provides encoding and decoding functions for the encodings specified in RFC 4648, which defines the Base16, Base32, and Base64 algorithms, and for the de-facto standard Ascii85 and Base85 encodings.

The RFC 4648 encodings are suitable for encoding binary data so that it can be safely sent by email, used as parts of URLs, or included as part of an HTTP POST request. The encoding algorithm is not the same as the uuencode program.

There are two interfaces provided by this module. The modern interface supports encoding bytes-like objects to ASCII bytes, and decoding bytes-like objects or strings containing ASCII to bytes. Both base-64 alphabets defined in RFC 4648 (normal, and URL- and filesystem-safe) are supported.

The legacy interface does not support decoding from strings, but it does provide functions for encoding and decoding to and from file objects. It only supports the Base64 standard alphabet, and it adds newlines every 76 characters as per RFC 2045. Note that if you are looking for RFC 2045 support you probably want to be looking at the email package instead.

Changed in version 3.3: ASCII-only Unicode strings are now accepted by the decoding functions of the modern interface.

Changed in version 3.4: Any bytes-like objects are now accepted by all encoding and decoding functions in this module. Ascii85/Base85 support added.

The modern interface provides:

base64.b64encode(s, altchars=None)

Encode the bytes-like object s using Base64 and return the encoded bytes.

Optional altchars must be a bytes-like object of length 2 which specifies an alternative alphabet for the + and / characters. This allows an application to e.g. generate URL or filesystem safe Base64 strings. The default is None, for which the standard Base64 alphabet is used.

May assert or raise a ValueError if the length of altchars is not 2. Raises a TypeError if altchars is not a bytes-like object.

base64.b64decode(s, altchars=None, validate=False)

Decode the Base64 encoded bytes-like object or ASCII string s and return the decoded