You can't have multiple constructors, but you can have multiple aptly-named factory methods.
class Document(object):
def __init__(self, whatever args you need):
"""Do not invoke directly. Use from_NNN methods."""
# Implementation is likely a mix of A and B approaches.
@classmethod
def from_string(cls, string):
# Do any necessary preparations, use the `string`
return cls(...)
@classmethod
def from_json_file(cls, file_object):
# Read and interpret the file as you want
return cls(...)
@classmethod
def from_docx_file(cls, file_object):
# Read and interpret the file as you want, differently.
return cls(...)
# etc.
You can't easily prevent the user from using the constructor directly, though. (If it is critical, as a safety precaution during development, you can analyze the call stack in the constructor and check that the call is made from one of the expected methods.)
