Save data in XML file in Python

I am trying to save my data to an XML file. This data comes from a website where I want to collect the reviews. There are always five reviews per page, which I want to save in XML format in a file. The problem is that if I print out the XML tree with print(ET.tostring(root, encoding='utf8').decode('utf8')) then there are all five reviews that I want to have. But if I save them into the file with tree.write("test.xml", encoding='unicode') then I only see one review... Here is my code:

import requests
from bs4 import BeautifulSoup
import re
import json
import xml.etree.cElementTree as ET

source = requests.get('https://www.tripadvisor.ch/Hotel_Review-g188113-d228146-Reviews-Coronado_Hotel-Zurich.html#REVIEWS').text

soup = BeautifulSoup(source, 'lxml')
pattern = re.compile(r'window.__WEB_CONTEXT__={pageManifest:(\{.*\})};')
script = soup.find("script", text=pattern)
dictData = pattern.search(script.text).group(1)
jsonData = json.loads(dictData)
	
def get_countrycitydata():

	countrycity_dict = dict()

	country_data = jsonData['urqlCache']['3960485871']['data']['locations']
	for data in country_data:
		data1 = data['parents']
		countrycity_dict["country_name"] = data1[2]['name']
		countrycity_dict["tripadvisorid_city"] = data1[0]['locationId']
		countrycity_dict["city_name"] = data1[0]['name']
			
	return countrycity_dict
	
def get_hoteldata():
	
	hotel_dict = dict()
	
	locations = jsonData['urqlCache']['669061039']['data']['locations']
	for data in locations:
		hotel_dict["tripadvisorid_hotel"] = data['locationId']
		hotel_dict["hotel_name"] = data['name']
			
	return hotel_dict
	
def get_reviews():	
	
	all_dictionaries = []
	
	for locations in jsonData['urqlCache']['669061039']['data']['locations']:
		for reviews in locations['reviewListPage']['reviews']:
		
			review_dict = {}
			
			review_dict["reviewid"] = reviews['id']
			review_dict["reviewurl"] =  reviews['absoluteUrl']
			review_dict["reviewlang"] = reviews['language']
			review_dict["reviewtitle"] = reviews['title']
			reviewtext = reviews['text']
			clean_reviewtext = reviewtext.replace('\n', ' ')
			review_dict["reviewtext"] = clean_reviewtext
	
			all_dictionaries.append(review_dict)
			
	return all_dictionaries

def xml_tree(new_dict): # should I change something here???
	
	root = ET.Element("countries")
	country = ET.SubElement(root, "country")
	
	ET.SubElement(country, "name").text = new_dict["country_name"]
	city = ET.SubElement(country, "city")
	
	ET.SubElement(city, "tripadvisorid").text = str(new_dict["tripadvisorid_city"])
	ET.SubElement(city, "name").text = new_dict["city_name"]
	hotels = ET.SubElement(city, "hotels")
	
	hotel = ET.SubElement(hotels, "hotel")
	ET.SubElement(hotel, "tripadvisorid").text = str(new_dict["tripadvisorid_hotel"])
	ET.SubElement(hotel, "name").text = new_dict["hotel_name"]
	reviews = ET.SubElement(hotel, "reviews")
	
	review = ET.SubElement(reviews, "review")
	ET.SubElement(review, "reviewid").text = str(new_dict["reviewid"])
	ET.SubElement(review, "reviewurl").text = new_dict["reviewurl"]
	ET.SubElement(review, "reviewlang").text = new_dict["reviewlang"]
	ET.SubElement(review, "reviewtitle").text = new_dict["reviewtitle"]
	ET.SubElement(review, "reviewtext").text = new_dict["reviewtext"]
	
	tree = ET.ElementTree(root)
	tree.write("test.xml", encoding='unicode')	
	
	print(ET.tostring(root, encoding='utf8').decode('utf8'))
	
##########################################################	

def main():

	city_dict = get_countrycitydata()
	hotel_dict = get_hoteldata()
	review_list = get_reviews()

	for index in range(len(review_list)):
		new_dict = {**city_dict, **hotel_dict, **review_list[index]}
	
		xml_tree(new_dict)

if __name__ == "__main__":
	main()	

How can I change the XML tree so that all five reviews are saved in the file? The XML file should look like this:

<countries>
	<country>
		<name>Schweiz</name>
		<city>
			<tripadvisorid>188113</tripadvisorid>
			<name>Zürich</name>
			<hotels>
				<hotel>
					<tripadvisorid>228146</tripadvisorid>
					<name>Hotel Coronado</name>
					<reviews>
						<review>
							<reviewid>672052111</reviewid> 
							<reviewurl>https://www.tripadvisor.ch/ShowUserReviews-g188113-d228146-r672052111-Coronado Hotel-Zurich.html</reviewurl>
							<reviewlang>de</reviewlang>
							<reviewtitle>Optimale Lage und Preis</reviewtitle>
							<reviewtext>Hervorragendes Hotel.Beste Erfahrun mit Service und Zimme.Die Qalität der Betten ist optimalr. Zimmer sind trotz geringer Größe sehr gut ausgestattet.Der Föhn war in diesem Fall (nicht in früheren)etwas lahm</reviewtext>
						</review>
                        <review>
                         second review here ...
                        </review>
                        <review>
                         third review here ...
                        </review>
                        ...
					</reviews>
				</hotel>
			</hotels>
		</city>
	</country>
</countries>

Thank you in advance for all suggestions!

Because your xml_tree(new_dict) exists inside of a for loop, the tree.write() method is being called multiple times overwriting your file.

Open your file in a (append) mode with open():

tree.write(open('test.xml', 'a'), encoding='unicode')

See documentation here