How to export the output of Python code into a csv file

Here you have the answer!

The data is stored in a dictionary and a csv is created appending the new data. If the file does not exists, the headers are added to the file.

I haven't tried the solution but the 'pseudocode' could help you with your requirements!

import os
import csv

user_api = os.environ['Api_key']
location = input("Vpišite ime mesta: ")

def Vremenska_napoved():
    """Za kraj, ki ga uporabnik vnese mu funkcija izpiše stanje vremena za tisti trenutek"""

    complete_api_link = "https://api.openweathermap.org/data/2.5/weather?q="+location+"&appid="+user_api
    api_link = requests.get(complete_api_link)
    api_data = api_link.json()

    if api_data ['cod'] == '404':
        print("Mesto ne obstaja: {}, Preverite pravilni vnos mesta za katerega želite vremensko napoved".format(location))
    else:
        #naredimo spremenljivke za shranjevanje in prikaz podatkov o vremenu
        Temperatura = ((api_data['main']['temp']) - 273.15)
        Vlažnost = api_data['main']['humidity']
        Hitrost_vetra = api_data['wind']['speed']
        Občuti_se_kot = api_data['weather'][0]['description']
        Datum_čas = datetime.now().strftime("%d %b %Y | %I:%M:%S %p")


        headers = ['Date', 'Temp', 'Hum', 'W_speed']
        filename = 'output.csv'
        file_exists = os.path.isfile(filename)

        row = {
            'Date': Datum_čas
            'Temp': Temperatura,
            'Hum': Vlažnost,
            'W_speed': Hitrost_vetra
        }
        
        a_file = open(filename, "a")
        dict_writer = csv.DictWriter(a_file, headers)

        if not file_exists:
            dict_writer.writeheader()  # file doesn't exist yet, write a header

        dict_writer.writerow(row)
        a_file.close())

        print ("_____________________________________________________________")
        print ("Vremenska napoved za - {} || {}".format(location.upper(), Datum_čas))
        print ("_____________________________________________________________")

        print ("Trenutna temperatura: {:.2f} stopinj C".format(Temperatura))
        print ("Trenutna vlažnost:",Vlažnost, '%')
        print ("Trenutna hitrost vetra:",Hitrost_vetra ,'km/h')
        print ("Občuti se kot:",Občuti_se_kot)

Vremenska_napoved()