如何将存储在变量中的Python字符串转换为字节序列？

Question

Very simple, I know, but the docs aren't too helpful. I'm trying to hash a simple string. I was following this guide. The example given therein is:

import hashlib
hash_object = hashlib.md5(b'Hello World')
print(hash_object.hexdigest())

And then you have a hash representation. Suppose I want to take this one step further. I have four strings I want to concatenate together, the result of which needs to be converted to byte sequence, in order to be passed to the hashlib.md5() function. However, I'm curious how I can replicate the b'Hello World' syntax using a variable instead of a hard-coded string. Docs seem to suggest you can pass in a format to the built-in format function, so for my use-case something like:

my_string = '%s%s%s%s' % (first, second, third, fourth)
byte_string = format(my_string, 'b')

This doesn't quite work, though. How do I do this?

Answer 1

Strings in Python are a sequence of characters, to convert a string to a sequence of bytes you encode it using some character set. For example:

my_string = '%s%s%s%s' % (first, second, third, fourth)
byte_string = my_string.encode('utf-8')

Instead of my_string.encode('utf-8') you could also use bytes(my_string, 'utf-8') , these are equivalent. You can also use a different encoding if you like, but UTF-8 is generally a good choice because it is capable of representing any code point (character) and it is fairly compact, especially for ASCII data.

Answer 2

my_string = '%s%s%s' % (first, second, third, fourth)
byte_string = bytes(my_string)