Bank

Well see, they wrote all this bank software, and, uh, to save space, they used two digits for the date instead of four. So, like, 98 instead of 1998? Uh, so I go through these thousands of lines of code and, uh... it doesn't really matter. I uh, I don't like my job, and, uh, I don't think I'm gonna go anymore.
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You know, corporate accounting is sure as hell gonna notice $305,326.13, Michael! - Office Space

Mission

Write a (user friendly) banking program that can view balances, deposit to, withdraw from, and transfer money between two or more account balances.

Details

• Two or more variables representing balances.
• Methods (functions) for display balance, deposit, withdraw, and transfer.
• Protection from silly logical flaws such as depositing a negative value.
• A main menu to select actions.

Example Program

Note: You will need to use globalization of vaiables for the sake of simplicity. (In Python, class-level variables can't be directly modified from methods, even if they're in the same class. (It is a silly language for silly people.))
Ex:
cab = 0  #checking account balance.
def deposit():
    global cab
    #<code for all the math-y type logical majinkas>
    cab += value_x  #value the user enters