[Tutor] [maryknauth at mac.com: Re: Input parameters for functions]

[David Rock]

Mary,

I've forwarded your reply to the mailing list. Remember to reply to the list
email and not individuals so others can see the conversation (both to help and
to learn).  Comments inline below

> ----- Forwarded message from Mary Knauth <maryknauth at mac.com> -----
> 
> Hello David,
> 
> Thanks very much for the welcome, I’ve written a couple question so far to the
> python tutor group, and it’s amazing what knowledge you all give back, so thank
> you!
> 
> Here is my code:
> 
> import sys
> 
> # -------------------------- DECLARE variables for balance, deposit, and withdrawal --------------------------
> 
> account_balance = float(500.25)                                                 # Starting balance indicated by Codio
> deposit_amount = 0                                                              # Declare variable 'deposit_amount'
> withdrawal_amount = 0                                                           # Declare variable 'withdrawal_amount'
> 
> 
> # -------------------------- DEFINE FUNCTIONS - balance, withdrawal, and deposit -----------------------------
> 
> def balance(account_balance):                                                   # Define balance function
>   print("Your current balance: ", account_balance)                              # Prints the current avalible balance
> 
> def deposit(account_balance, deposit_amount):                                   # Define DEPOSIT function with parameters account_balance and deposit_amount
>   deposit_amount = float(input("How much would you like to deposit today?\n"))  # Accept user input for the deposit amount, in float format
>   balance = account_balance + deposit_amount                                    # This addition assigns the updated value of the account blance, to the variable 'BALANCE'
>   print("Deposit was $%.2f , your new current balance is $%.2f" % (deposit_amount, balance))  # Prints depost amount and account balance
> 
> def withdrawal(account_balance, withdrawal_amount):                             # Define WITHDRAWAL function with parameters account_balance and withdrawal_amount
>   withdrawal_amount = float(input("How much would you like to withdraw today?\n")) #  Accept user input for the withdrawal amount, in float format
>   if withdrawal_amount > account_balance:                                       # Checking to see if the amount requested, is greater than the amount avalible
>     print("Insuffient funds, $%.2f is greater than your account balance of $%.2f" % (withdrawal_amount, account_balance)) # If the amount requested is greater than the account balance, there are insuffient funds
>   else:                                                                         # Suffient amount of funds are avalible, the function continues
>     balance = account_balance - withdrawal_amount                               # Variable 'balance' is assigned to reflect the new avalible balance
>     print ("Withdrawal amount was $%.2f, your new current balance is $%.2f" % (withdrawal_amount, balance))  # Prints withdrawal amount and account balance


These are mostly fine for individual use-cases, but all they do is print
the temporary updated value.  For deposit and withdrawal, do you have a
requirement to remember the new values?  How would you update the global
variables with the new values from the functions to make them persistent? 


> # ------------------------------------ ACCEPT USER INPUT - D, B, W, or Q -------------------------------------
> userChoice = 'go'                                                               # Setting the variable 'userChoice' to 'go', so we can impliment a while loop
> 
> while userChoice != 'E':                                                        # As long as the user does not select 'E' (Exit), the program will keep looping with user choices
> 
> # Step ONE =>  Ask user what action they would like to proceed with, user input is accepted and assigned to the variable 'userchoice'
>     userChoice = input ("Would you like to check your (B)alance, make a (D)eposit, (W)ithdraw cash, or (E)xit?\n").upper()
> 
> # Step TWO => conditional statement begins based on the value of variable 'userchoice' from user input
> # Four branches ustilizing if / elif for DEPOSIT, BALANCE, WITHDRAWAL, EXIT
>     if (userChoice == 'D'):                                                     # Accepts input D and proceeds with function 'deposit'
>         deposit (account_balance, deposit_amount)                               # DEPOSIT function is called with parameters 'account_balance' and 'deposit_amount'
> 
>     elif (userChoice == 'B'):                                                   # Accepts input B and proceeds with function 'balance'
>         balance (account_balance)                                               # BALANCE function is called with parameter 'account_balance'
> 
>     elif (userChoice == 'W'):                                                   # Accepts input D and proceeds with function 'withdrawal'
>         withdrawal (account_balance, withdrawal_amount)                         # WITHDRAWAL function is called with parameters 'account_balance' and 'withdrawal_amount'
> 
>     elif (userChoice == 'E'):                                                   # Accepts input E for EXIT
>         print("Thank you for banking with us.")                                 # There is no function for EXIT, and therefore the user has a printed message ending their session


Overall, This is structured just fine.  The main thing I would look at
is what I mentioned above regarding value permanence.  To see what I
mean, run the program, but make several transactions in a row.  If you
subtract $100 and then check your balance, does it change?  If not, how
would you fix it?


-- 
David Rock
david at graniteweb.com