new feature: support mode argument in op.open in python binding correctly

[TennyZhuang]

Feature Description

The Python binding implements open method on Operator instance, and it's generally expected that the behavior should be compatible with the builtin open function. Unfortunately, it's wrong when handling the mode argument.

The following arguments are valid for the mode argument:

ref: https://www.manpagez.com/man/3/fopen/

r Open text file for reading. The stream is positioned at the
beginning of the file.
r+ Open for reading and writing. The stream is positioned at the
beginning of the file.
w Truncate to zero length or create text file for writing. The
stream is positioned at the beginning of the file.
w+ Open for reading and writing. The file is created if it does not
exist, otherwise it is truncated. The stream is positioned at
the beginning of the file.
a Open for writing. The file is created if it does not exist. The
stream is positioned at the end of the file. Subsequent writes
to the file will always end up at the then current end of file,
irrespective of any intervening fseek(3) or similar.
a+ Open for reading and writing. The file is created if it does not
exist. The stream is positioned at the end of the file. Subse-
quent writes to the file will always end up at the then current
end of file, irrespective of any intervening fseek(3) or similar.

Then in Python 3, all above modes represent TEXT mode, and all read/write methods accept str as arguments. An optional character t or b can be attached with the above modes, means TEXT and BINARY.

It seems that opendal treat them all as BINARY mode. It's the default behavior, and opendal will not reject invalid modes that it can't support.

Problem and Solution

There are several actions can be taken for the purpose.

• Reject a and + in modes due to lack of support by the object store interface.
• Introduce enum IoMode { Text, Binary } to support b argument.
• Considering change the default behavior from rb to rt.

Additional Context

No response

Are you willing to contribute to the development of this feature?

• Yes, I am willing to contribute to the development of this feature.