base64
— Base16、Base32、Base64、Base85 数据编码
¶
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 RFC 3548 interfaces provided by this module. The modern interface supports encoding and decoding ASCII byte string objects using all three RFC 3548 defined alphabets (normal, URL-safe, and filesystem-safe). Additionally, the decoding functions of the modern interface also accept Unicode strings containing only ASCII characters. The legacy interface provides for encoding and decoding to and from file-like objects as well as byte strings, but only using the Base64 standard alphabet.
3.3 版改变： 现在，现代接口解码函数可以接受仅 ASCII 的Unicode 字符串。
3.4 版改变： 任何 像字节对象 s are now accepted by all encoding and decoding functions in this module. Ascii85/Base85 support added.
现代接口提供：
base64.
b64encode
(
s
,
altchars=None
)
¶
Encode a byte string using Base64.
s
is the string to encode. Optional
altchars
must be a string of at least length 2 (additional characters are ignored) 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
，使用标准 Base64 字母。
The encoded byte string is returned.
base64.
b64decode
(
s
,
altchars=None
,
validate=False
)
¶
Decode a Base64 encoded byte string.
s
is the byte string to decode. Optional
altchars
must be a string of at least length 2 (additional characters are ignored) which specifies the alternative alphabet used instead of the
+
and
/
字符。
The decoded string is returned. A
binascii.Error
异常被引发，若
s
被不正确填充。
若
validate
is
False
(the default), non-base64-alphabet characters are discarded prior to the padding check. If
validate
is
True
, non-base64-alphabet characters in the input result in a
binascii.Error
.
base64.
standard_b64encode
(
s
)
¶
Encode byte string s using the standard Base64 alphabet.
base64.
standard_b64decode
(
s
)
¶
Decode byte string s using the standard Base64 alphabet.
base64.
urlsafe_b64encode
(
s
)
¶
Encode byte string
s
using a URL-safe alphabet, which substitutes
-
而不是
+
and
_
而不是
/
in the standard Base64 alphabet. The result can still contain
=
.
base64.
urlsafe_b64decode
(
s
)
¶
Decode byte string
s
using a URL-safe alphabet, which substitutes
-
而不是
+
and
_
而不是
/
in the standard Base64 alphabet.
base64.
b32encode
(
s
)
¶
Encode a byte string using Base32. s is the string to encode. The encoded string is returned.
base64.
b32decode
(
s
,
casefold=False
,
map01=None
)
¶
Decode a Base32 encoded byte string.
s
is the byte string to decode. Optional
casefold
is a flag specifying whether a lowercase alphabet is acceptable as input. For security purposes, the default is
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
不是
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.
The decoded byte string is returned. A
binascii.Error
被引发若
s
is incorrectly padded or if there are non-alphabet characters present in the string.
base64.
b16encode
(
s
)
¶
Encode a byte string using Base16.
s is the string to encode. The encoded byte string is returned.
base64.
b16decode
(
s
,
casefold=False
)
¶
Decode a Base16 encoded byte string.
s
is the string to decode. Optional
casefold
is a flag specifying whether a lowercase alphabet is acceptable as input. For security purposes, the default is
False
.
The decoded byte string is returned. A
TypeError
被引发若
s
were incorrectly padded or if there are non-alphabet characters present in the string.
base64.
a85encode
(
s
,
*
,
foldspaces=False
,
wrapcol=0
,
pad=False
,
adobe=False
)
¶
Encode a byte string using Ascii85.
s is the string to encode. The encoded byte string is returned.
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 (
'\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 string 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.
3.4 版新增。
base64.
a85decode
(
s
,
*
,
foldspaces=False
,
adobe=False
,
ignorechars=b' \t\n\r\v'
)
¶
Decode an Ascii85 encoded byte string.
s is the byte string to decode.
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 controls whether the input sequence is in Adobe Ascii85 format (i.e. is framed with <~ and ~>).
ignorechars should be a byte string containing characters to ignore from the input. This should only contain whitespace characters, and by default contains all whitespace characters in ASCII.
3.4 版新增。
base64.
b85encode
(
s
,
pad=False
)
¶
Encode a byte string using base85, as used in e.g. git-style binary diffs.
若 pad is true, the input is padded with “\0” so its length is a multiple of 4 characters before encoding.
3.4 版新增。
base64.
b85decode
(
b
)
¶
Decode base85-encoded byte string. Padding is implicitly removed, if necessary.
3.4 版新增。
注意
Both Base85 and Ascii85 have an expansion factor of 5 to 4 (5 Base85 or Ascii85 characters can encode 4 binary bytes), while the better-known Base64 has an expansion factor of 6 to 4. They are therefore more efficient when space expensive. They differ by details such as the character map used for encoding.
传统接口：
base64.
decode
(
input
,
output
)
¶
Decode the contents of the binary
input
file and write the resulting binary data to the
output
文件。
input
and
output
必须为
文件对象
.
input
will be read until
input.read()
returns an empty bytes object.
base64.
decodebytes
(
s
)
¶
base64.
decodestring
(
s
)
¶
Decode the byte string
s
, which must contain one or more lines of base64 encoded data, and return a byte string containing the resulting binary data.
decodestring
is a deprecated alias.
3.1 版新增。
base64.
encode
(
input
,
output
)
¶
Encode the contents of the binary
input
file and write the resulting base64 encoded data to the
output
文件。
input
and
output
必须为
文件对象
.
input
will be read until
input.read()
returns an empty bytes object.
encode()
returns the encoded data plus a trailing newline character (
b'\n'
).
base64.
encodebytes
(
s
)
¶
base64.
encodestring
(
s
)
¶
Encode the byte string
s
, which can contain arbitrary binary data, and return a byte string containing one or more lines of base64-encoded data.
encodebytes()
returns a string containing one or more lines of base64-encoded data always including an extra trailing newline (
b'\n'
).
encodestring
is a deprecated alias.
模块的用法范例：
>>> import base64 >>> encoded = base64.b64encode(b'data to be encoded') >>> encoded b'ZGF0YSB0byBiZSBlbmNvZGVk' >>> data = base64.b64decode(encoded) >>> data b'data to be encoded'
另请参阅