如何在 python 中编码为 Base64？

Question

Hey I am trying to encode something to base64 but I am getting an invalid format error I have no idea why maybe someone can help me:)

creqBytes = bytes(f'{"threeDSServerTransID":threeDSServerTransID,"transStatus":"Y","acsTransID":acsTransID,"messageType":"CRes","messageVersion":"2.1.0"}', 'utf-8')
creq2 = base64.b64encode(creqBytes).decode("ascii")
print(creq2)

Answer 1

The ValueError: Invalid format specifier error message you are getting is from your first line. This is because you have an f before the string indicates that this will be a string with f-string formatting in it. However, you haven't put any f-string formatting in the string. Hence the error message.

I was able to get this to run by removing the f . Here is my test:

import base64

creqBytes = bytes('{"threeDSServerTransID":threeDSServerTransID,"transStatus":"Y","acsTransID":acsTransID,"messageType":"CRes","messageVersion":"2.1.0"}', 'utf-8')
print(creqBytes)
# b'{"threeDSServerTransID":threeDSServerTransID,"transStatus":"Y","acsTransID":acsTransID,"messageType":"CRes","messageVersion":"2.1.0"}'

creq2 = base64.b64encode(creqBytes).decode("ascii")
print(creq2)
# eyJ0aHJlZURTU2VydmVyVHJhbnNJRCI6dGhyZWVEU1NlcnZlclRyYW5zSUQsInRyYW5zU3RhdHVzIjoiWSIsImFjc1RyYW5zSUQiOmFjc1RyYW5zSUQsIm1lc3NhZ2VUeXBlIjoiQ1JlcyIsIm1lc3NhZ2VWZXJzaW9uIjoiMi4xLjAifQ==

However, I suspect that isn't what you are trying to do. My guess would be that you have some variables in Python that you want to include in the string. If that is the case then the f-string would look like:

import base64

threeDSServerTransID = 2
acsTransID = 3

creqBytes = bytes(f'{{"threeDSServerTransID":{threeDSServerTransID},"transStatus":"Y","acsTransID":{acsTransID},"messageType":"CRes","messageVersion":"2.1.0"}}', 'utf-8')
print(creqBytes)
# b'{"threeDSServerTransID":2,"transStatus":"Y","acsTransID":3,"messageType":"CRes","messageVersion":"2.1.0"}'
creq2 = base64.b64encode(creqBytes).decode("ascii")
print(creq2)
# eyJ0aHJlZURTU2VydmVyVHJhbnNJRCI6MiwidHJhbnNTdGF0dXMiOiJZIiwiYWNzVHJhbnNJRCI6MywibWVzc2FnZVR5cGUiOiJDUmVzIiwibWVzc2FnZVZlcnNpb24iOiIyLjEuMCJ9

That formatting of the f-string looks like it would be error prone and difficult for other people to read. I suspect that having the data as a Python dictionary and outputting it to a JSON format before then doing base64 encoding might be easier to understand and read. This would look like:

import base64
import json

threeDSServerTransID = 2
acsTransID = 3

var1 = {
    "threeDSServerTransID": threeDSServerTransID,
    "transStatus": "Y",
    "acsTransID": acsTransID,
    "messageType": "CRes",
    "messageVersion": "2.1.0"
}
var2 = json.dumps(var1)
print(var2)
# '{"threeDSServerTransID": 2, "transStatus": "Y", "acsTransID": 3, "messageType": "CRes", "messageVersion": "2.1.0"}'

var3 = base64.b64encode(var2.encode())
print(var3)
# b'eyJ0aHJlZURTU2VydmVyVHJhbnNJRCI6IDIsICJ0cmFuc1N0YXR1cyI6ICJZIiwgImFjc1RyYW5zSUQiOiAzLCAibWVzc2FnZVR5cGUiOiAiQ1JlcyIsICJtZXNzYWdlVmVyc2lvbiI6ICIyLjEuMCJ9'
print(var3.decode('ascii'))
# eyJ0aHJlZURTU2VydmVyVHJhbnNJRCI6IDIsICJ0cmFuc1N0YXR1cyI6ICJZIiwgImFjc1RyYW5zSUQiOiAzLCAibWVzc2FnZVR5cGUiOiAiQ1JlcyIsICJtZXNzYWdlVmVyc2lvbiI6ICIyLjEuMCJ9