Flask 'tuple' object 在保存文件时没有属性 'write'

Question

I am getting this wired error on flask when I want to save a file received on a post request. I tried debugging but I do not understand the error because I use flask save, and on google and other stack overflow questions I found that this has to to with python file API like missing open or wrong flags, but I do not have any flags, or do not need to open any file here.

How I sent the file:

const uploadFile = async (file) =>{
  const formData = new FormData();
  formData.append("file", file);
  fetch("http://localhost:5000/files/upload", {method: "POST", body: formData});
}

How I recive the file:

@app.route('/files/upload', methods = ['POST'])
def recive_upload_file():
    file = request.files['file']
    filename = file.filename
    root_dir = os.path.dirname(os.getcwd())
    file.save((os.path.join(root_dir,'backend', 'upload'), filename))
    return "done"

As far as I can tell the file is sending correctly because if I try to print the filename in the recive_uploaded_file function I get the correct name.

The Error:

Traceback (most recent call last):
  File "c:\Python37\lib\site-packages\flask\app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "c:\Python37\lib\site-packages\flask\app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "c:\Python37\lib\site-packages\flask_cors\extension.py", line 161, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "c:\Python37\lib\site-packages\flask\app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "c:\Python37\lib\site-packages\flask\_compat.py", line 39, in reraise
    raise value
  File "c:\Python37\lib\site-packages\flask\app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "c:\Python37\lib\site-packages\flask\app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "index.py", line 239, in upload_file
    file.save((os.path.join(root_dir,'backend', 'upload'), filename))
  File "c:\Python37\lib\site-packages\werkzeug\datastructures.py", line 3070, in save
    copyfileobj(self.stream, dst, buffer_size)
  File "c:\Python37\lib\shutil.py", line 82, in copyfileobj
    fdst.write(buf)
AttributeError: 'tuple' object has no attribute 'write'

Answer 1

I found the issue. I had the wrong path, the filename should be inside os.path.join()

file.save((os.path.join(root_dir,'backend', 'upload', filename)))

Answer 2

The file path you specified is incorrect. You're trying to write to a tuple as file path:

>>> root_dir =  '/root/'
>>> filename = 'test.png'
>>> (os.path.join(root_dir,'backend', 'upload'), filename)
('/root/backend/upload', 'test.png')

You should move the filename inside the os.path.join call.

>>> os.path.join(root_dir,'backend', 'upload', filename)
'/root/backend/upload/test.png'