[Feature Request] Add path.getsize or file.getsize methods

[tairov]

Review Mojo's priorities

• [X] I have read the roadmap and priorities and I believe this request falls within the priorities.

What is your request?

Mojo v0.4.0 now supports file module, but it seems that we still need one essential function -- getsize or filesize With native Mojo file module we have to load whole file into memory just to know its size.

    var f_ = open(file_name, "r")
    let data = f_.read()
    let cp_size = data._buffer.size

What is your motivation for this change?

So far in llama2.🔥 we have to use workaround via Python.

    let _os = Python.import_module("os")
    let ff_size = _os.path.getsize(file_name)
    let cp_size = string.atol(ff_size.to_string())

It's turned out newcomers to Mojo who are trying to run llama2 locally, got multiple issues because of misconfiguration with MOJO_PYTHON_LIBRARY, etc.

It would be great to add getsize or filesize to file or path modules in the next release.

Any other details?

In Python it's implemented in path module

    let _os = Python.import_module("os")
    let ff_size = _os.path.getsize(file_name)

I think it's worthwhile to implement the more general os.stat , since fs_stat must provide more details about file, but I'm not sure what are the concerns regarding platforms compatiblity.

# python alternatives
os.path.getsize()
os.stat()