Create Your First Python Currency Converter

Building a currency converter in Python is an excellent way to dive into real-world applications of programming, especially in the financial technology space. Whether you're a beginner or an experienced developer, creating a functional app that pulls live foreign exchange rates offers both educational value and practical utility. In this guide, you’ll learn how to build a fully interactive currency converter using Python, Streamlit, and a live forex API—no front-end experience required.

What Is a Currency Converter App?

A currency converter app is a digital tool that allows users to convert the value of one currency into another based on current exchange rates. These tools are essential for travelers, international businesses, investors, and developers working on financial applications.

Thanks to modern APIs and user-friendly Python libraries, you can now build a real-time currency converter in under 100 lines of code. The app will fetch live exchange rates, perform accurate conversions, and display results instantly—perfect for sharing with teams or deploying publicly.

Why Use Python and Streamlit?

Python has become the go-to language for rapid prototyping and data-driven applications. When combined with Streamlit, a powerful open-source framework, you can transform simple scripts into interactive web apps with minimal effort.

👉 Discover how easy it is to bring your Python projects to life with the right tools.

Key Benefits of Streamlit:

No HTML, CSS, or JavaScript required
Real-time updates with live data
Easy deployment and sharing
Ideal for developers, analysts, and fintech enthusiasts

This makes Streamlit the perfect choice for building and sharing your Python currency converter without getting bogged down by complex web development.

What You’ll Need to Build the App

Before diving into the code, ensure you have the following:

Python installed (version 3.7 or higher)
A free API key from a forex data provider (we’ll use TraderMade in this example)
Streamlit library installed via pip
Basic understanding of Python functions and APIs

With these in place, you're ready to start coding.

Step-by-Step: Building the Currency Converter

Step 1: Install Required Libraries

Open your terminal and install Streamlit:

pip install streamlit requests

These packages will allow you to create the web interface (streamlit) and make HTTP requests to fetch live exchange rates (requests).

Step 2: Import Libraries and Set Up API Connection

Start your Python script by importing the necessary modules and defining your API credentials:

import streamlit as st
import requests

base_url = "https://marketdata.tradermade.com/api/v1/convert"
api_key = "YOUR_API_KEY"  # Replace with your actual key

🔐 Never share your API key publicly. For deployment, consider using environment variables.

Step 3: Add a Logo (Optional)

Enhance your app’s appearance by adding a logo. Save the image file (e.g., logo.png) in the same directory and use:

st.image("logo.png", width=200)

You can skip this or replace it with any branding element relevant to your project.

Step 4: Create the Currency Conversion Function

This function takes an amount, source currency, and target currency, then returns the exchange rate and converted total:

def convert_currency(amount, from_currency, to_currency):
    url = f"{base_url}?api_key={api_key}&from={from_currency}&to={to_currency}&amount={amount}"
    response = requests.get(url)
    if response.status_code == 200:
        data = response.json()
        rate = data["quote"]
        converted_amount = data["total"]
        return rate, converted_amount
    else:
        return None, None

This core logic powers the entire app—accurate, fast, and reliable.

Step 5: Fetch Supported Currencies

To provide users with a dropdown menu of valid currencies, fetch the list dynamically:

def fetch_supported_currencies():
    url = "https://marketdata.tradermade.com/api/v1/live_currencies_list?api_key=YOUR_API_KEY"
    response = requests.get(url)
    if response.status_code == 200:
        data = response.json()
        if "available_currencies" in data:
            return list(data["available_currencies"].keys())
        else:
            st.write("Error: Currency list not available.")
            return None
    else:
        st.write(f"API Error: {response.status_code}")
        return None

This ensures your app always displays up-to-date currency options.

Step 6: Build the User Interface

Now create the main app interface using Streamlit components:

def currency_converter():
    st.title("🌍 Real-Time Currency Converter")

    amount = st.number_input("Enter amount:", min_value=1, value=100, step=1)
    supported_currencies = fetch_supported_currencies()

    if supported_currencies:
        from_currency = st.selectbox("From:", supported_currencies, index=supported_currencies.index("EUR"))
        to_currencies = st.multiselect("To:", supported_currencies, default=["USD"])

        if st.button("Convert"):
            st.subheader("Results")
            for to_currency in to_currencies:
                try:
                    rate, converted = convert_currency(amount, from_currency, to_currency)
                    if rate:
                        st.success(f"✅ {amount} {from_currency} = {converted:.2f} {to_currency}")
                        st.info(f"Exchange Rate: 1 {from_currency} = {rate:.4f} {to_currency}")
                    else:
                        st.error(f"Failed to convert {from_currency} to {to_currency}")
                except Exception as e:
                    st.error(f"Error: {str(e)}")

The interface is intuitive: input amount, choose currencies, click “Convert,” and view results instantly.

Step 7: Run the App Locally

Save your file as currency_converter.py and run:

streamlit run currency_converter.py

Your app will launch in your browser at http://localhost:8501.

👉 Turn your idea into an interactive web app in minutes—see what’s possible.

Frequently Asked Questions (FAQ)

Q: Can I use this currency converter offline?
A: No. The app requires an internet connection to fetch live exchange rates from the API.

Q: Is Streamlit free to use?
A: Yes. Streamlit is open-source and free for personal and commercial projects.

Q: How often are exchange rates updated?
A: Rates are pulled in real time with each conversion request, ensuring accuracy.

Q: Can I deploy this app online?
A: Absolutely. You can deploy it on Streamlit Community Cloud, AWS, or any hosting platform that supports Python.

Q: Are there alternatives to the TraderMade API?
A: Yes—other options include ExchangeRate-API, Fixer.io, and Alpha Vantage—but always verify their free tier limits and usage policies.

Q: How do I protect my API key when sharing the app?
A: Use environment variables or Streamlit’s secrets management feature to keep sensitive data secure.

Final Thoughts

You’ve now built a fully functional Python currency converter that leverages real-time forex data and delivers a polished user experience—all without writing a single line of front-end code. This project not only strengthens your Python skills but also introduces you to APIs, web deployment, and practical fintech tools.

Whether you're analyzing global markets or helping colleagues calculate travel budgets, this app serves as a foundation for more advanced financial tools.

👉 Start building smarter financial applications today—unlock the power of real-time data.

With minimal setup and maximum impact, this project proves that powerful tools don’t need to be complicated. Expand it further by adding features like historical charts, dark mode, or multi-language support—and keep coding!