[okasaki]

> But, having null checks here and there makes your code unreadable.

    if user is not None:                                                                                                                                                                                                                                                                                                                                    
         balance = user.get_balance()                                                                                                                                                                                                                                                                                                                       
         if balance is not None:                                                                                                                                                                                                                                                                                                                            
             balance_credit = balance.credit_amount()                                                                                                                                                                                                                                                                                                       
             if balance_credit is not None and balance_credit > 0:                                                                                                                                                                                                                                                                                          
                 can_buy_stuff = True                                                                                                                                                                                                                                                                                                                       
    else:                                                                                                                                                                                                                                                                                                                                                   
        can_buy_stuff = False                                                                                                                                                                                                                                                                                                                               
                                                                                                                                                                                                                                                                                                                                                            

Actually I think that's very readable

    user: Optional[User]                                                                                                                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                                                                                                                                            
    can_buy_stuff: Maybe[bool] = Maybe.from_value(user).map(  # type hint is not required                                                                                                                                                                                                                                                                   
        lambda real_user: real_user.get_balance(),                                                                                                                                                                                                                                                                                                          
    ).map(                                                                                                                                                                                                                                                                                                                                                  
        lambda balance: balance.credit_amount(),                                                                                                                                                                                                                                                                                                            
    ).map(                                                                                                                                                                                                                                                                                                                                                  
        lambda balance_credit: balance_credit > 0,                                                                                                                                                                                                                                                                                                          
    )                                                                                                                                                                                                                                                                                                                                                       
                                                                                                                                                                                                                                                                                                                                                            
    Much better, isn't it?                                                                                                                                                                                                                                                                                                                                  
                                                                                                                                                                                                                                                                                                                                                            

No?!? That's much worse.

[cellularmitosis]

Yeah, I'd much rather read this:

    def can_buy_stuff(user):
        if user is None:
            return False
        balance = user.get_balance()
        if balance is None:
            return False
        balance_credit = balance.credit_amount()
        if balance_credit is None:
            return False
        return balance_credit > 0

Edit: something like Swift's optionals and nil-coalescing syntax might make this easier to read:

   def can_buy_stuff(user):
       return (user?.get_balance()?.credit_amount() ?? 0) > 0