TKInter not working when I code in a function

I am writing a short program that uses a flight api. For what I am trying to do, I want lines 30 to 59(where "Client" is, to right before "root.mainloop") to be inside the function flightInfo. When I have the code formatted as it is right now(see below) , the tkinter window I am using for my GUI works fine. However when I move the api code (30-59) inside the function, my TKinter window does not open. Any assistance would be appreciated! I don't see why moving the api code(30-59) messes with the tkinter window. Thank You

Link to image of the code

from duffel_api import Duffel
from tkinter import *
root = Tk()
def flightInfo():
client = Duffel(access_token="token")
destination = input("\nWhere do you want to go?\n").strip()
origin = input("\nFrom where?\n").strip()
departure_date = input("\nOn what date? (YYYY-MM-DD)\n").strip()
print("\nSearching flights...")
slices = [
{
"origin": origin,
"destination": destination,
"departure_date": departure_date,
},
]
offer_request = (
client.offer_requests.create()
.passengers([{"type": "adult"}])
.slices(slices)
.return_offers()
.execute()
)
offers = offer_request.offers
for idx, offer in enumerate(offers):
print(
f"{idx + 1}. {offer.owner.name} flight departing at "
+ f"{offer.slices[0].segments[0].departing_at} "
+ f"{offer.total_amount} {offer.total_currency}"
)
destLabel = Label(root, text = "Where do want to go?")
destLabel.grid(row=0,column=0)
dest = Entry(root)
dest.grid(row=0,column=1)
srcLabel = Label(root, text = "From Where?")
srcLabel.grid(row=1,column=0)
src = Entry(root)
src.grid(row=1,column=1)
dateLabel = Label(root, text = "On what date? (YYYY-MM-DD)")
dateLabel.grid(row=2,column=0)
date = Entry(root)
date.grid(row=2,column=1)
submit = Button(root,text = "Submit",command= flightInfo)
submit.grid(row=3,column=0)
root.mainloop

Notice below that this minimal code will open a window.

If no window is opening, the code may be in an infinite loop.

I suggest starting adding widgets from the original code step by step to find the issue.

from tkinter import *
root = Tk()
root.mainloop()

It might even be better to start from this code.
This way, at least the program starts with one widget working.

import tkinter as tk
root = tk.Tk()
label = tk.Label(root, text="I Exist!")
label.pack()
root.mainloop()

I'm glad my comment solved your problem (I've written it here as a formal answer for others to see if you want to upvote it).

The solution is that root.mainloop requires brackets, so it would look like:

> root.mainloop()