how to export a variable value only based on half of a condition, but not the other?-CodePudding

I have this exercise, which I need to decrease a class attributes value(value always >=0), and then restore back to original value. I try to count only the times "-= 1", but if the method keeps operate, then I cannot get the right "count". Please see the code:

# Tee ratkaisusi tähän:
class DecreasingCounter:
    def __init__(self, initial_value: int): 
        self.value = initial_value
    def print_value(self):
        print("value:", self.value)
    def decrease(self):
        global count
        count = 0
        if self.value > 0:
            self.value -= 1
            count  = 1
        else: 
            self.value == 0 

    def set_to_zero(self):
        self.value -= self.value
        return True
    def reset_original_value(self):
        self.value  = count

    # Write the rest of the methods here!
if __name__ == "__main__":
    counter = DecreasingCounter(5)
    counter.decrease()
    counter.decrease()
    counter.decrease()
    counter.print_value()
    counter.reset_original_value()
    counter.print_value()

as you can see when run counter.decrease() the third time, my count back to be "0".

How do I export a right count?

CodePudding user response：

You are quite close! But look what happens with your count:

    def decrease(self):
        global count
        count = 0 # Here!

Every decrease you set count to 0 at first, so count is always 0 or 1. What you want to do is just move it outside the class:

count = 0
class DecreasingCounter:
    ...

But now you need to remember about reseting that count!

    def reset_original_value(self):
        global count
        self.value  = count
        count = 0

But if there is a reason it is a global variable? If not, you can just use instance attribute for that:

class DecreasingCounter:
    def __init__(self, initial_value: int):
        self.value = initial_value
        self.count = 0
        # or instead of counting calls, use the current_value directly
        self.current_value = initial_value

CodePudding user response：

I think it would be simpler to just explicitly maintain both the current and initial values:

class DecreasingCounter:
    def __init__(self, initial_value: int): 
        self.initial_value = initial_value
        self.value = initial_value

    def print_value(self):
        print("value:", self.value)

    def decrease(self):
        if self.value > 0:
            self.value -= 1

    def set_to_zero(self):
        self.value = 0

    def reset_original_value(self):
        self.value = self.initial_value

Now you can do:

if __name__ == "__main__":
    counter = DecreasingCounter(5)

    counter.decrease()
    counter.decrease()
    counter.decrease()
    counter.print_value()

    counter.reset_original_value()
    counter.print_value()

    counter.set_to_zero()
    counter.print_value()

    counter.decrease()
    counter.print_value()

Giving:

value: 2
value: 5
value: 0
value: 0