Update currency_calculator.py (#318)

Key Points:

•	Input Handling: The program takes the base currency and the currency to exchange into from the user. If the input is blank, the loop exits.
•	Cache: The program uses a cache to store exchange rates for USD and EUR. If the rate is already in the cache, it retrieves it; otherwise, it fetches the rate from the API.
•	Exchange Rate API: The rates are fetched from floatrates.com in JSON format.
•	Currency Conversion: The amount is exchanged based on the cached or newly fetched rate, and the result is displayed.

Author: BrahmajitMohapatra

Currency Script/currency_calculator.py

@@ -1,37 +1,55 @@
+# Importing necessary modules for currency formatting and HTTP requests
 from locale import currency
 import requests
 import json
 
-currency = input().lower()
+# Get the base currency input from the user and convert it to lowercase
+currency = input("Enter the base currency (e.g., USD, EUR): ").lower()
+
+# Initialize an empty cache to store exchange rates
 cache = {}
 
+# Infinite loop to process exchange requests until the user exits
 while True:
 
-    currency_exch = input().lower()
+    # Get the target currency input from the user and convert it to lowercase
+    currency_exch = input("Enter the currency to exchange to (leave blank to exit): ").lower()
 
+    # If the input is blank, break out of the loop (exit condition)
     if currency_exch == '':
         break
 
-    amount_to_exch = int(input())
+    # Get the amount to exchange from the user
+    amount_to_exch = int(input("Enter the amount to exchange: "))
 
+    # URL for getting exchange rates from floatrates.com
     URL = f'http://www.floatrates.com/daily/{currency}.json'
 
+    # Fetch the exchange rates in JSON format
     exch = json.loads(requests.get(URL).text)
 
+    # Update cache for USD and EUR based on the base currency
     if currency == 'usd':
+        # If base currency is USD, cache EUR rate
         cache.update(eur=exch['eur']['rate'])
     elif currency == 'eur':
+        # If base currency is EUR, cache USD rate
         cache.update(usd=exch['usd']['rate'])
     else:
+        # For other base currencies, cache both USD and EUR rates
         cache.update(usd=exch['usd']['rate'], eur=exch['eur']['rate'])
 
     print("Checking the cache...")
+
+    # Check if the target currency's rate is in the cache
     if currency_exch in cache:
+        # If the rate is in the cache, calculate the exchanged amount
         rate = round(amount_to_exch * cache[currency_exch], 2)
         print("Oh! It is in the cache!")
         print(f"You received {rate} {currency_exch.upper()}.")
     else:
-        #print("Sorry, but it is not in the cache!")
+        # If the rate is not in the cache, fetch it from the exchange rates and store it in cache
+        print("Sorry, but it is not in the cache!")
         cache[currency_exch] = exch[currency_exch]['rate']
         rate = round(amount_to_exch * cache[currency_exch], 2)
         print(f"You received {rate} {currency_exch.upper()}.")