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Use Tkinter for the desktop interface and the forex-python package for exchange-rate conversion. The example below accepts an amount and two currency codes, converts the amount when you click a button, and displays input or service errors in the window.
What you need
- Python installed in the environment where you will run the program.
- Tkinter available for that Python installation.
- The
forex-pythonpackage installed in the same environment.
Install the package from a terminal with:
python -m pip install forex-pythonIf your system uses a different Python command, use that command consistently for both installation and running the app. Tkinter is Python’s interface to Tcl/Tk; the official documentation explains that its classes wrap Tcl/Tk commands and recommends Tkinter variables such as StringVar for associating values with widgets: Python 3.14.8 Tkinter documentation.
Build the converter
Save this as currency_converter.py, then run it with Python. Enter standard three-letter currency codes supported by the service, such as USD and INR.
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1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesimport tkinter as tk
from forex_python.converter import CurrencyRates
rates = CurrencyRates()
def convert_currency():
amount_text = amount_var.get().strip()
from_code = from_var.get().strip().upper()
to_code = to_var.get().strip().upper()
try:
amount = float(amount_text)
except ValueError:
result_var.set("Enter a valid number for the amount.")
return
if not from_code or not to_code:
result_var.set("Enter both currency codes.")
return
try:
converted = rates.convert(from_code, to_code, amount)
except Exception as error:
result_var.set(f"Could not convert: {error}")
return
result_var.set(f"{amount:,.2f} {from_code} = {converted:,.2f} {to_code}")
root = tk.Tk()
root.title("Currency Converter")
root.resizable(False, False)
amount_var = tk.StringVar(value="1")
from_var = tk.StringVar(value="USD")
to_var = tk.StringVar(value="INR")
result_var = tk.StringVar(value="Enter an amount and currency codes.")
pad = {"padx": 10, "pady": 6}
tk.Label(root, text="Amount").grid(row=0, column=0, sticky="w", **pad)
tk.Entry(root, textvariable=amount_var, width=24).grid(row=0, column=1, **pad)
tk.Label(root, text="From currency").grid(row=1, column=0, sticky="w", **pad)
tk.Entry(root, textvariable=from_var, width=24).grid(row=1, column=1, **pad)
tk.Label(root, text="To currency").grid(row=2, column=0, sticky="w", **pad)
tk.Entry(root, textvariable=to_var, width=24).grid(row=2, column=1, **pad)
tk.Button(root, text="Convert", command=convert_currency).grid(
row=3, column=0, columnspan=2, pady=8
)
tk.Label(root, textvariable=result_var, wraplength=320, justify="left").grid(
row=4, column=0, columnspan=2, sticky="w", **pad
)
root.mainloop()How the code works
Connect the interface to Tkinter variables
StringVar instances hold the amount, currency codes, and result text. The entry widgets use textvariable to read and update those values. Tkinter variables wrap Tcl variables, providing a convenient link between a widget and a Python value.
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Validate before making a request
The callback first converts the amount text to a number. If the entry is blank or contains text that cannot be parsed as a float, it updates the result label and returns without calling the service. It also checks that both currency-code fields are nonempty. A nonempty code is not necessarily supported, so service errors are handled separately.
Convert and display the amount
CurrencyRates() creates the client, and convert(from_code, to_code, amount) asks it to convert the entered amount. The try/except around the request keeps a failed request from crashing the interface and puts the error in the result label. The display formats both amounts to two decimal places; that is display rounding, not a change to the rate returned by the package.
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Use a separate rate lookup when you need the rate
If the interface should show the exchange rate itself or apply it using custom logic, call get_rate and multiply the amount:
rate = rates.get_rate(from_code, to_code)
converted = amount * rateFor a simple amount converter, convert is more direct. The package documents both methods and examples at forex-python usage.
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Choose floating-point or Decimal arithmetic
The example uses the package’s default floating-point behavior, which keeps input handling simple. For monetary arithmetic where decimal representation matters, initialize the client with force_decimal=True and pass a Decimal amount consistently:
from decimal import Decimal
from forex_python.converter import CurrencyRates
rates = CurrencyRates(force_decimal=True)
converted = rates.convert("USD", "INR", Decimal("10.45"))Do not pass a normal float or integer amount to a client configured this way: the package documentation says mixing those values with Decimal mode raises DecimalFloatMismatchError. See the package’s usage examples and project repository.
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Understand what the displayed conversion means
The result is an informational conversion from the package’s configured rate source, not a guaranteed live quote or a promise of the rate available for a transaction. The package documentation identifies ratesapi.io as its source, while its PyPI description refers to theratesapi.com and rates published by the European Central Bank. Those descriptions differ, so the sources do not establish a current update schedule or service guarantee. Check the package version and its current service behavior before relying on a rate for a time-sensitive use: forex-python on PyPI.
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