Loop to add more input

Question

I have 3 more cars that I have but I need to know how to loop things like the car input so it will allow you to input it again if you do the wrong input same thing with the extras so they have to be either 1 or 0.

print("===================================================") 
print("==============Car Finance Calculations=============") 
print(" Choose your veicle: ")
print(" SUV type 1 ")
print(" Hatch type 2 ")
print(" Sedan type 3 ")
print("===================================================")
caaaaaaaar = int(input(" Please enter Which car you want to finance: "))
years = int(input(" enter years of loan either 3 or 4 or 5 Years: "))      
if caaaaaaaar == 1:                                             
    carsvalue = int(input("Please enter you cars value: "))    
    residual = carsvalue * 0.30                                               
    financing = carsvalue - residual                            
    print(" financing value for the car is: ", round(financing,2))      
    print(" Intrest rate is 9% ")                               
    n = years * 12                                              
    r = 9 / (100 * 12)                                         
    Financingcost = financing * ((r*((r+1)**n))/(((r+1)**n)-1)) 
    print(" Your Montly financing rate is: ", round(Financingcost,2))    
    print("================================================================================")
    print("Please Choose extras: ")                                   
    print("======================================================")
    print(" If you would like fuel type 1 if not type 0")
    print(" If you would like insurance type 1 if not type 0")
    print(" if you would like Maintenance type 1 if not type 0")

    print("======================================================")

    if caaaaaaaar == 1:
        x, y, z = [int(x) for x in input("Enter Your extras with spaces:").split()] 

    print("=======================================")

    if x == 1:                                           
        print("Yes you want fuel")                       
        fuelcost = 80 * 4.33                            
        print("fuel cost is", round(fuelcost,2))                  
 
    if x == 0:                                           
        print("you dont want fuel as an extra")          
        fuelcost = 0                                    
        print("Fuel cost is: ", fuelcost)               

    print("=======================================")   

    if y == 1:                                          
        print("yes you want insurance")                  
        insurancecost = (1200 / 12)                      
        print("Insurance cost is: ", round(insurancecost,2))      

    if y ==0:                                            
        print("you dont want insurance")                 
        insurancecost = 0                                
        print("insurance cost is: ",insurancecost)       

    print("=======================================")     

    if z == 1:                                          
        print("yes you want maintenance")               
        maintenancecost = (100 * 1)                     
        print("Maintenance cost is: ", round(maintenancecost,2))  

    if z == 0:                                           
        print("you dont want maintenance")              
        maintenancecost = 0                              
        print("maintenance cost is: ",maintenancecost)   
    print("=======================================")
  

    total_cost_for_extras = fuelcost + maintenancecost + insurancecost       
    print("Total cost for the selected extras is: ", round(total_cost_for_extras,2))  
    TOTALFOREVERYTHING = total_cost_for_extras + Financingcost              
    print("Total monthly financing rate is: ", round(TOTALFOREVERYTHING,2))          

Answer 1

My recommendation is to take a functional approach to this problem. You are calling int(input()) multiple times and want to validate the user input before proceeding on to the next lines each time. You can do this in a function that will continue to loop until the input is confirmed as valid. Once the input is validated, you can exit the function's frame by returning the value using the return key word.

# This is the function definition. 
# The code in this function does not execute until the function is called.
def prompt_int(
        text,
        minimum=0,
        maximum=1,
        error="The value you entered is not valid try again."
):
    # when the function is called it will start a second while loop that will keep looping
    # until valid input is entered
    while True:
        try:
            val = int(input(text))
            if minimum <= val <= maximum:
                return val
            raise ValueError
        except ValueError:
            print(error)


# This is the outer while loop. It will keep looping forever if the user so chooses.
while True:
    # instead of calling print() a bunch one option is to assign a docstring to a variable
    car_prompt = '''
===================================================
==============Car Finance Calculations=============
Choose your veicle:
SUV: 1
Hatch: 2
Sedan: 3
===================================================
Please enter the number for the car you want to finance or 0 to exit:\n
'''
    # This is where we first call the function. 
    # Our docstring will be passed into the function to be used as a prompt.
    # We also pass in some args for maximum and minimum params
    caaaaaaaar = prompt_int(car_prompt, 0, 3)
    # 0 is false so we can exit the while loop if the user enters 0
    if not caaaaaaaar:
        break
    year_prompt = "Enter years of the car loan (3, 4 or 5):\n"
    years = prompt_int(year_prompt, 3, 5)

    if caaaaaaaar == 1:
        val_prompt = "Please enter you cars value:\n"
        carsvalue = prompt_int(val_prompt, 0, 2147483647)
        residual = carsvalue * 0.30
        financing = carsvalue - residual

        print("Financing value for the car is: ", round(financing, 2))
        print("Intrest rate is 9% ")

        n = years * 12
        r = 9 / (100 * 12)
        Financingcost = financing * ((r * ((r + 1) ** n)) / (((r + 1) ** n) - 1))

        print(" Your Montly financing rate is: ", round(Financingcost, 2))
        print("================================================================================")
        print("Please Choose extras: ")
        print("======================================================")
        x = prompt_int("If you would like fuel type 1 else type 0:\n")
        y = prompt_int("If you would like insurance type 1 else type 0:\n")
        z = prompt_int("If you would like Maintenance type 1 else type 0:\n")
        print("======================================================")

        if x == 1:
            print("Yes you want fuel")
            fuelcost = 80 * 4.33
            print("fuel cost is", round(fuelcost, 2))
        else:
            print("you dont want fuel as an extra")
            fuelcost = 0
            print("Fuel cost is: ", fuelcost)

        print("=======================================")

        if y == 1:
            print("yes you want insurance")
            insurancecost = (1200 / 12)
            print("Insurance cost is: ", round(insurancecost, 2))
        else:
            print("you dont want insurance")
            insurancecost = 0
            print("insurance cost is: ", insurancecost)

        print("=======================================")

        if z == 1:
            print("yes you want maintenance")
            maintenancecost = (100 * 1)
            print("Maintenance cost is: ", round(maintenancecost, 2))
        else:
            print("you dont want maintenance")
            maintenancecost = 0
            print("maintenance cost is: ", maintenancecost)
        print("=======================================")

        total_cost_for_extras = fuelcost + maintenancecost + insurancecost
        print("Total cost for the selected extras is: ", round(total_cost_for_extras, 2))
        TOTALFOREVERYTHING = total_cost_for_extras + Financingcost
        print("Total monthly financing rate is: ", round(TOTALFOREVERYTHING, 2))
    elif caaaaaaaar == 2:
        # Put your code for car 2 in this block. 
        # If it is like car 1 code except the value of a few variables 
        # then make another func 
        pass
    else:
        # Car 3 code...
        pass

Answer 2

I suggest that you put your vehicle types in a dictionary:

vehicle_type_dict = {
    1: "SUV type",
    2: "Hatch type",
    3: "Sedan type"
}

and do a while-loop to check if your input is in the dictionary:

while True:
    caaaaaaaar = int(input(" Please enter Which car you want to finance: "))

    if caaaaaaaar not in vehicle_type_dict:
        continue #loop again if input not in the dictionary

    #read next line of code if input is in the dictionary

    #do something below if input is correct

    years = int(input(" enter years of loan either 3 or 4 or 5 Years: "))

    break #end loop

Answer 3

As per my understanding of the question you want to run an iteration until the user gives the right answer.

In that case, you can use flag variable in while.

flag = False
while(flag is False):
    if(condition_statisfied):
        flag = True

Answer 4

You want to use a while loop. Like this:

carsEntered = 0
while (carsEntered <= 4):
    caaaaaaaar = int(input(" Please enter Which car you want to finance: "))
    years = int(input(" enter years of loan either 3 or 4 or 5 Years: "))
    carsEntered += 1

You could also use a for loop instead but that depends on what you want to do.