如何用小写替换大写并放置下划线？ 我的错误是什么？

Question

I am trying to write two functions. The first is to change it:

HjhfdhHbvUj

to this

hjhfdh_hbv_uj

And the second function should do the opposite.

def camel_snake(str_name):
    str_name.replace(([a-z][A-Z]+)|([A-Z]+[a-z]), '\L$1')
    return str_name

def snake_camel(str_name):
    str_name.replace('\L$1', ([a-z][A-Z]+)|([A-Z]+[a-z]))
    return str_name

Please tell me how to arrange so that I do not have an error in the syntax?

My teacher forbade me to use regular expressions to solve this problem. Please give me some links to read something that will help solve this problem

Answer 1

I am trying to write two functions. The first is to change it:

HjhfdhHbvUj

to this

hjhfdh_hbv_uj

And the second function should do the opposite.

def camel_snake(str_name):
    str_name.replace(([a-z][A-Z]+)|([A-Z]+[a-z]), '\L$1')
    return str_name

def snake_camel(str_name):
    str_name.replace('\L$1', ([a-z][A-Z]+)|([A-Z]+[a-z]))
    return str_name

Please tell me how to arrange so that I do not have an error in the syntax?

My teacher forbade me to use regular expressions to solve this problem. Please give me some links to read something that will help solve this problem