Update app.py

app.py

@@ -12,7 +12,15 @@ interest_rate = st.number_input("Interest rate (%):")
 months = int(st.number_input("Number of months:", step=1))
 
 # Calculate the present value
-present_value = (monthly_payment * 12 / interest_rate) * (1 - (1 / (1 + interest_rate/12)**months))
+if interest_rate == 0:
+    st.error("Interest rate cannot be zero.")
+    st.stop()
+
+try:
+    present_value = (monthly_payment * 12 / interest_rate) * (1 - (1 / (1 + interest_rate/12)**months))
+except ZeroDivisionError:
+    st.error("Please enter a non-zero interest rate.")
+    st.stop()
 
 # Display the present value
 st.write(f"The present value is {present_value:,.2f} using the discrete model")
@@ -30,4 +38,4 @@ plt.xlabel("Period")
 plt.ylabel("Cashflow")
 for i, cf in enumerate(cf_df.cashflows):
     plt.annotate(f"{cf:,.2f}", (i, cf), textcoords="offset points", xytext=(0, months), ha="center")
-st.pyplot(plt)
+st.pyplot(plt)