@app.route('/api/v1.0/download/getfile')
def stream_file():
file_name = app.config['MY_DATA_ROOT'] + "/test.txt"
def generate():
    f = open(file_name)
    while True:
        line = f.readline()
        if line.startswith("last line"):
            break
        else:
            yield line.encode('utf-8')


return app.response_class(generate(), mimetype='application/octet-stream')

getFile() {
    let options = new RequestOptions({responseType: ResponseContentType.Blob});
    return this.http.get(this.getFileURL, options)
    .map((response: Response) => {return <Blob>response.blob();});
}

onDownloadButtonClicked(): void {
    this.genService.getFile()
    .subscribe(fileData => {FileSaver.saveAs(fileData, "test.txt");});

  }