import re
 
def convert(name):
    return re.sub(r'([A-Z]*)([A-Z][a-z]+)', lambda x: (x.group(1) + '_' if x.group(1) else '') + x.group(2) + '_', name).rstrip('_').lower()
 
def camel_to_snake(name):
    return re.sub(r"(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])", '_', name).lower()
 
print convert('CamelCase')
print convert('HTTP')
print convert('HTTPRequest')
print convert('SecureHTTPRequest')
print convert('SecureHTTP')
 
print camel_to_snake('CamelCase')
print camel_to_snake('HTTP')
print camel_to_snake('HTTPRequest')
print camel_to_snake('SecureHTTPRequest')
print camel_to_snake('SecureHTTP')

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