#Route

@app.route('/input_dokumen', methods = ['GET','POST']) # MAIN FUNCTION
def dokumen():
    if request.method == 'POST':
        doc = request.files['fileIn']
        out = docxFile.somefunction(doc)
        return render_template ("Input_Dokumen.html", output = out)
    else:
        return render_template("Input_Dokumen.html")

#TextArea

<textarea id="output" rows="10" cols="75" readonly value= "{{output}}"></textarea>