Python base64 模块

概览

Base64 使用 64 个可打印字符表示二进制数据，常用于基于文本的传输协议、在 JSON/XML/HTML 中内嵌资源，以及 HTTP Basic 认证等场景。标准字母表为 A–Z a–z 0–9 + /，使用 = 作为填充； URL 安全变体用 - _ 替代 + /。

主要 API（`import base64`）

b64encode(data: bytes, altchars: bytes | None = None) -> bytes
b64decode(data: bytes | str, altchars: bytes | None = None, validate: bool = False) -> bytes
standard_b64encode / standard_b64decode (force the standard alphabet)
urlsafe_b64encode / urlsafe_b64decode (URL/filename-safe variant)
b32encode / b32decode, b16encode / b16decode
a85encode / a85decode, b85encode / b85decode (ASCII85/Base85)

快速示例

字符串编码/解码（UTF-8）

import base64

text = "Hello, world"
raw = text.encode("utf-8")

b64 = base64.b64encode(raw)          # bytes
print(b64)                            # b'SGVsbG8sIHdvcmxk'

plain = base64.b64decode(b64)
print(plain.decode("utf-8"))         # Hello, world

URL 安全的 Base64

import base64

raw = b"token:id/123+scope"
url_b64 = base64.urlsafe_b64encode(raw)
print(url_b64)                        # b'dG9rZW46aWQvMTIzK3Njb3Bl'

print(base64.urlsafe_b64decode(url_b64))  # b'token:id/123+scope'

严格校验解码

import base64, binascii

try:
	base64.b64decode(b"@@invalid@@", validate=True)
except binascii.Error as exc:
	print("Decode failed:", exc)

文件 I/O

import base64

# Binary file → Base64 text
with open("input.bin", "rb") as f:
	encoded = base64.b64encode(f.read()).decode("ascii")
with open("output.txt", "w", encoding="ascii") as f:
	f.write(encoded)

# Base64 text → binary file
with open("output.txt", "r", encoding="ascii") as f:
	data = base64.b64decode(f.read())
with open("restored.bin", "wb") as f:
	f.write(data)

ASCII85 / Base85

a85encode/a85decode 与 b85encode/b85decode 提供更高密度的编码（常见于 PostScript 与 PDF），接收与返回的均为 bytes，并可配置分组与压缩等选项。

import base64

data = b"hello base85"
a85 = base64.a85encode(data)
b85 = base64.b85encode(data)
print(a85, b85)
print(base64.a85decode(a85))
print(base64.b85decode(b85))

提示：更多细节与边界情况请参考官方文档： https://docs.python.org/3/library/base64.html。