Python从base64转换为二进制

Question

我在将 base64 编码字符串转换为二进制时遇到问题。我正在以下链接中收集 Fingerprint2D，

url = "https://pubchem.ncbi.nlm.nih.gov/rest/pug/compound/cid/108770/property/Fingerprint2D/xml"

Fingerprint2D=AAADccB6OAAAAAAAAAAAAAAAAAAAAAAAAAA8WIEAAAAAAACxAAAAHgAACAAADAzBmAQwzoMABgCI AiTSSACCCAAhIAAAiAEMTMgMJibMsZuGeijn4BnI+YeQ0OMOKAACAgAKAABQAAQEABQAAAAAAAAA AA==

Pubchem中的descriptiong说这是115字节的字符串，转换成二进制应该是920位。我尝试使用以下命令将其转换为二进制文件，

    response = requests.get(url)
    tree = ET.fromstring(response.text)

    for el in tree[0]:
        if "Fingerprint2D" in el.tag:
            fpp = bin(int(el.text, 16))
            print(len(fpp))

如果我使用上面的代码，我会收到以下错误，“值错误:使用 base16 的 int() 的无效文字:

如果我使用下面的代码，fpp(二进制)的长度等于 1278，这不是我所期望的。

    response = requests.get(url)
    tree = ET.fromstring(response.text)

    for el in tree[0]:
        if "Fingerprint2D" in el.tag:
            fpp = bin(int(hexlify(el.text), 16))
            print(len(fpp))

非常感谢!!

Answer 1

要解码 base64 格式，您需要将 bytes 对象传递给 base64.decodebytes 函数:

import base64

t = "AAADccB6OAAAAAAAAAAAAAAAAAAAAAAAAAA8WIEAAAAAAACxAAAAHgAACAAADAzBmAQwzoMABgCI AiTSSACCCAAhIAAAiAEMTMgMJibMsZuGeijn4BnI+YeQ0OMOKAACAgAKAABQAAQEABQAAAAAAAAA AA==".encode("ascii")

decoded = base64.decodebytes(t)

print(decoded)
print(len(decoded)*8)

我得到以下信息:

b'\x00\x00\x03q\xc0z8\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00<X\x81\x00\x00\x00\x00\x00\x00\xb1\x00\x00\x00\x1e\x00\x00\x08\x00\x00\x0c\x0c\xc1\x98\x040\xce\x83\x00\x06\x00\x88\x02$\xd2H\x00\x82\x08\x00! \x00\x00\x88\x01\x0cL\xc8\x0c&&\xcc\xb1\x9b\x86z(\xe7\xe0\x19\xc8\xf9\x87\x90\xd0\xe3\x0e(\x00\x02\x02\x00\n\x00\x00P\x00\x04\x04\x00\x14\x00\x00\x00\x00\x00\x00\x00\x00'
920

所以 920 位符合预期。

要获取二进制数据，只需迭代字节并使用 format 和零填充到 8 位(bin 添加 0b header 所以它不合适)，然后 join 字符串:

print("".join(["{:08b}".format(x) for x in decoded]))

结果:

00000000000000000000001101110001110000000111101000111000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000011110001011000100000010000000000000000000000000000000000000000000000001011000100000000000000000000000000011110000000000000000000001000000000000000000000001100000011001100000110011000000001000011000011001110100000110000000000000110000000001000100000000010001001001101001001001000000000001000001000001000000000000010000100100000000000000000000010001000000000010000110001001100110010000000110000100110001001101100110010110001100110111000011001111010001010001110011111100000000110011100100011111001100001111001000011010000111000110000111000101000000000000000001000000010000000000000101000000000000000000101000000000000000001000000010000000000000101000000000000000000000000000000000000000000000000000000000000000000

(如预期的那样是 920 个字符)