unable to call function in Flask

[verb]

Hello everyone
i am trying to call function from another function but unfortunately it doesn't work
here is my code... The app starts and it doesn't ask for dir name as i was expecting

from flask import Flask,render_template
from os import listdir
from os.path import join,isfile

app = Flask(__name__)

def ask_for_dir():
    dirpath=raw_input("please provide dirname for gallery")
    spisak={}
    for i in listdir(dirpath):
        pat=join(dirpath,i)
        if isfile(pat) and pat.endswith("jpg") or pat.endswith("jpeg"):
            spisak[i]=pat
        else:
            continue
    return spisak

@app.route('/')
def hello_world():
    spisak=ask_for_dir()
    lensp=len(spisak)
    return render_template("gal2.html",lensp=lensp,spisak=spisak)


if __name__ == '__main__':
    app.run(debug=True)