How to use a value from first method in second method (in the same class)?-CodePudding

I want to use the d value from can_add method for add method, but get error 'MoneyBox' object has no attribute 'd'. How to use d value for add method?

class MoneyBox:
    def __init__(self, capacity = 0):
        self.capacity = capacity

    def can_add(self, v):
        self.v = v
        if self.capacity > self.v:
            self.d = True
            return d
        else:
            self.d = False
            return self.d
        
    def add(self, v):
        self.can_add(v)
        if self.d == True:
            self.v  = v
        f = self.capacity - self.v
        return f

a = MoneyBox(10)
a.add(5)

CodePudding user response：

d isn't a variable of the class but only in can_add method hence you can't access it in add method.
more so, you don't need it anyway, just return true/false.

class MoneyBox:
    def __init__(self, capacity = 0):
        self.capacity = capacity

    def can_add(self, v):
        if self.capacity > v:
            return True
        else:
            return False
        
    def add(self, v):
        if self.can_add(v) == True:
            v  = v
        f = self.capacity - v
        return f

a = MoneyBox(10)
a.add(5)

CodePudding user response：

You are trying to return a class variable when you want to return a local variable.

class MoneyBox:
    def __init__(self, capacity = 0):
        self.capacity = capacity

    def can_add(self, v):
        self.v = v
        if self.capacity > self.v:
            d = True
            return d
        else:
            d = False
            return d
        
    def add(self, v):
        d = self.can_add(v)
        if d == True:
            self.v  = v
        f = self.capacity - self.v
        return f

a = MoneyBox(10)
a.add(5)

If you want the value to be saved in a class variable you can do it like this

class MoneyBox:
    def __init__(self, capacity = 0):
        self.capacity = capacity
        self.d = False

    def can_add(self, v):
        self.v = v
        if self.capacity > self.v:
            self.d = True
            
        else:
            self.d = False
            
        
    def add(self, v):
        self.can_add(v)
        if self.d == True:
            self.v  = v
        f = self.capacity - self.v
        return f

a = MoneyBox(10)
a.add(5)

CodePudding user response：

You don't need the can_add method to return anything since when you call it in add, self.d attribute is already updated. So just change can_add to the following and everything will work as expected:

def can_add(self, v):
    self.v = v
    if self.capacity > self.v:
        self.d = True
    else:
        self.d = False

That being said, I strongly suggest initializing all class instance variables in __init__ so that your definitions are all in one place and it's more readable. So like:

def __init__(self, capacity = 0):
        self.capacity = capacity
        self.v = None
        self.d = None