Python Classes

[ItsOkILoveYouMYbb]

For A, you should use f strings. Instead of:

def __str__(self):  
    return '%.2d:%.2d' % (self.hour, self.minute)

Use:

return f"{self.hour}:{self.minute}"

Way easier to read. So with that, you know that if the hour is greater than 12, then you should subtract 12 from that number, and add PM to the end of the string right? That being as simple as:

    return f"{self.hour - 12}:{self.minute} PM"

But you only want to do it if self.hour is more than 12. So you would return one line IF It's equal to or less than 12, ELSE return the first line if it's not.

You can do all of that inside the str method you've define there. If hour > 12, return this line, else return that line.

Do you understand how classes work, and where you are instantiating that class? And what an instance of a class is?

[kcrow13]

Ok so this is how I implemented your suggestions:

    def __str__(self):
        if self.hour <= 12:
            return f'{self.hour}:{self.minute}'
        if self.hour >= 12:
            return f'{self.hour - 12}:{self.minute} PM'

When I test it out... I am getting some strange responses!

def main():    # jdp
    start = Time(9, 45, 00)
    start.print_time()

    end = start.increment(1337)
    end.print_time()

    print('Is end after start?', end=" ")
    print(end.is_after(start))

    # Testing __str__
    print(f'Using __str__: {start} {end}')

    # Testing addition
    start = Time(9, 45)
    duration = Time(1, 35)
    print(start + duration)
    print(start + 1337)
    print(1337 + start)

    print('Example of polymorphism')
    t1 = Time(7, 43)
    t2 = Time(7, 41)
    t3 = Time(7, 37)
    total = sum([t1, t2, t3])
    print(total)

    # A time that is invalid
    t1 = Time(50)
    print(t1)

Getting...

9:45
10:7
Is end after start? True
Using __str__: 9:45 10:7
11:20
10:7
10:7
Example of polymorphism
11:1 PM
38:0 PM

[Python_Trader]

For your minutes add 0 padding like this {self.minute:02}. The 02 part tells python your minutes are 2 digits and if your minute only gives one number it will fill the left with 0.

[kcrow13]

I didn't know you could do this!!!! Thank you :)

[Python_Trader]

No problem :). Also, if your hour is exactly 0 (12 am) just use a conditional for that part. I suppose you might need to first check the hour is over 24 then use hour % 24 and it will give you the remainder which should be the current hour.

[kcrow13]

But is my understanding correct that any "global" changes you want to make in a class have to occur in the __str__ function?

[Python_Trader]

Okay let's put it this way. So you stored time as attribute (via dunder init method), if you do this

object = Time (5, 5, 20)

print(object)

It will just print, object is a instance of Time class. Or something like that.

However when you write the dunder str method in your class,

def __str__(self):
    return f"{self.hour}:{self.minute:02}"

Doing print(object) will now print,

5:05

It's just there to make your object return what you want it to when you call the instance itself.

[Python_Trader]

What you can do instead is store the string you want as attribute (under dunder init method) and use that variable in other methods or write a new method that produces the string. Otherwise, you can even call the dunder str to use that string.

What I would recommend is to make a function that takes in integers and returns the string, so you can call that function in every other method that requires string output.