# `base64` — Codificações de dados em Base16, Base32, Base64, Base85

Código-fonte: 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 3548, which defines the Base16, Base32, and Base64 algorithms, and for the de-facto standard Ascii85 and Base85 encodings.

The RFC 3548 encodings are suitable for encoding binary data so that it can 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 3548 (normal, and URL- and filesystem-safe) are supported.

A interface legada não oferece suporte a decodificação de strings, mas fornece funções para codificação e decodificação de e para objetos arquivo. Ele oferece suporte a apenas o alfabeto padrão Base64 e adiciona novas linhas a cada 76 caracteres conforme RFC 2045. Note que se você estiver procurando por suporte para RFC 2045 você provavelmente vai querer conferir o pacote `email`.

Alterado na versão 3.3: Strings Unicode exclusivamente ASCII agora são aceitas pelas funções de decodificação da interface moderna.

Alterado na versão 3.4: Quaisquer objetos bytes ou similares agora são aceitos por todas as funções de codificação e decodificação neste módulo. Adicionado suporte a ASCII85/Base85.

A interface moderna oferece:

`base64.``b64encode`(s, altchars=None)

  Codifica o objeto bytes ou similar s usando Base64 e retorna o `bytes` codificado.

  Os altchars opcionais devem ser um objeto bytes ou similar de pelo menos comprimento 2 (caracteres adicionais são ignorados) que especifica um alfabeto alternativo para os caracteres `+` e `/`. Isso permite que um aplicativo, por exemplo, gerar strings Base64 seguras para URL ou sistema de arquivos. O padrão é `None`, para o qual o alfabeto Base64 padrão é usado.

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

  Decodifica o objeto bytes ou similar ou string ASCII s codificada em Base64 e retorna o `bytes` decodificado.

  Altchars opcionais devem ser um objeto bytes ou similar ou string ASCII de pelo menos 2 (caracteres adicionais são ignorados) que especifica o alfabeto alternativo usado ao invés do `+` e `/` caracteres.

  A `binascii.Error` exception is raised if s is incorrectly padded.

  If validate is `False` (the default), characters that are neither in the normal base-64 alphabet nor the alternative alphabet are discarded prior to the padding check. If validate is `True`, these non-alphabet characters in the input result in a `binascii.Error`.

`base64.``standard_b64encode`(s)

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

`base64.``standard_b64decode`(s)

  Decode bytes-like object or ASCII string s using the standard Base64 alphabet and return the decoded `bytes`.

`base64.``urlsafe_b64encode`(s)

  Encode bytes-like object s using the URL- and filesystem-safe alphabet, which substitutes `-` instead of `+` and `_` instead of `/` in the standard Base64 alphabet, and return the encoded `bytes`. The result can still contain `=`.

`base64.``urlsafe_b64decode`(s)

  Decode bytes-like object or ASCII string s using the URL- and filesystem-safe alphabet, which substitutes `-` instead of `+` and `_` instead of `/` in the standard Base64 alphabet, and return the decoded `bytes`.

`base64.``b32encode`(s)

  Encode the bytes-like object s using Base32 and return the encoded `bytes`.

`base64.``b32decode`(s, casefold=False, map01=None)

  Decode the Base32 encoded bytes-like object or ASCII string s and return the decoded `bytes`.

  casefold opcional é uma flag especificando se um alfabeto minúsculo é aceitável como entrada. Por razões de segurança, o padrão é `False`.

  RFC 3548 allows for optional mapping of the digit 0 (zero) to the letter O (oh), and for optional mapping of the digit 1 (one) to either the letter I (eye) or letter L (el). The optional argument map01 when not `None`, specifies which letter the digit 1 should be mapped to (when map01 is not `None`, the digit 0 is always mapped to the letter O). For security purposes the default is `None`, so that 0 and 1 are not allowed in the input.

  A `binascii.Error` is raised if s is incorrectly padded or if there are non-alphabet characters present in the input.

`base64.``b16encode`(s)

  Encode the bytes-like object s using Base16 and return the encoded `bytes`.

`base64.``b16decode`(s, casefold=False)

  Decode the Base16 encoded bytes-like object or ASCII string s and return the decoded `bytes`.

  casefold opcional é uma flag especificando se um alfabeto minúsculo é aceitável como entrada. Por razões de segurança, o padrão é `False`.

  A `binascii.Error` is raised if s is incorrectly padded or if there are non-alphabet characters present in the input.

`base64.``a85encode`(b, *, foldspaces=False, wrapcol=0, pad=False, adobe=False)

  Encode the bytes-like object b using Ascii85 and return the encoded `bytes`.

  foldspaces is an optional flag that uses the special short sequence ‘y’ instead of 4 consecutive spaces (ASCII 0x20) as supported by ‘btoa’. This feature is not supported by the “standard” Ascii85 encoding.

  wrapcol controls whether the output should have newline (`b'\n'`) characters added to it. If this is non-zero, each output line will be at most this many characters long.

  pad controls whether the input is padded to a multiple of 4 before encoding. Note that the `btoa` implementation always pads.

  adobe controls whether the encoded byte sequence is framed with `<~` and `~>`, which is used by the Adobe implementation.

  Novo na versão 3.4.

`base64.``a85decode`(b, *, foldspaces=False, adobe=False, ignorechars=b' \t\n\r\v')

  Decode the Ascii85 encoded bytes-like object or ASCII string b and return the decoded `bytes`.

  foldspaces is a flag that specifies whether the ‘y’ short sequence should be accepted as shorthand for 4 consecutive spaces (ASCII 0x20). This feature is not supported by the “standard” Ascii85 encoding.

  adobe controla se a entrada está no formato Adobe Ascii85 (ou seja, cercada por <~ e ~>).

  ignorechars should be a bytes-like object or ASCII string containing characters to ignore from the input. This should only contain whitespace characters, and by default contains all whitespace characters in ASCII.

  Novo na versão 3.4.

`base64.``b85encode`(b, pad=False)

  Encode the bytes-like object b using base85 (as used in e.g. git-style binary diffs) and return the encoded `bytes`.

  If pad is true, the input is padded with `b'\0'` so its length is a multiple of 4 bytes before encoding.

  Novo na versão 3.4.

`base64.``b85decode`(b)

  Decode the base85-encoded bytes-like object or ASCII string b and return the decoded `bytes`. Padding is implicitly removed, if necessary.

  Novo na versão 3.4.

A interface legada:

`base64.``decode`(input, output)

  Decode the contents of the binary input file and write the resulting binary data to the output file. input and output must be file objects. input will be read until `input.readline()` returns an empty bytes object.

`base64.``decodebytes`(s)

  Decode the bytes-like object s, which must contain one or more lines of base64 encoded data, and return the decoded `bytes`.

  Novo na versão 3.1.

`base64.``decodestring`(s)

  Deprecated alias of `decodebytes()`.

  Obsoleto desde a versão 3.1.

`base64.``encode`(input, output)

  Encode the contents of the binary input file and write the resulting base64 encoded data to the output file. input and output must be file objects. input will be read until `input.read()` returns an empty bytes object. `encode()` inserts a newline character (`b'\n'`) after every 76 bytes of the output, as well as ensuring that the output always ends with a newline, as per RFC 2045 (MIME).

`base64.``encodebytes`(s)

  Encode the bytes-like object s, which can contain arbitrary binary data, and return `bytes` containing the base64-encoded data, with newlines (`b'\n'`) inserted after every 76 bytes of output, and ensuring that there is a trailing newline, as per RFC 2045 (MIME).

  Novo na versão 3.1.

`base64.``encodestring`(s)

  Deprecated alias of `encodebytes()`.

  Obsoleto desde a versão 3.1.

Um exemplo de uso do módulo:

    >>> import base64
    >>> encoded = base64.b64encode(b'data to be encoded')
    >>> encoded
    b'ZGF0YSB0byBiZSBlbmNvZGVk'
    >>> data = base64.b64decode(encoded)
    >>> data
    b'data to be encoded'

Ver também

Módulo `binascii`

  Módulo de suporte contendo conversões ASCII para binário e binário para ASCII.

RFC 1521 - MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies

  Section 5.2, “Base64 Content-Transfer-Encoding,” provides the definition of the base64 encoding.