Pygame 2D : rotation around center not working properly

Question

here is the code I use to rotate an image around its center:

class Square:
    def __init__(self) :
        self.x, self.y, self.angle = 50, 200, 0
        self.image = load('redrect.png')
        self.image360 = pygame.transform.rotate(self.image, self.angle)
        ...

    def blit(self):
        self.image360 = pygame.transform.rotate(self.image, self.angle)
        # I made a center() function to calculate the center of an image/rect 
        self.center360 = center(self.x, self.y, self.image360)
        MyScreen.blit(self.image360, self.center360)

mysquare = Square()

while 1:
    for e in events:
        if e.type == KEYDOWN:
            if e.key == K_r:
                mysquare.angle += 45

When I run the code and attempt to rotate the square, I notice that the rotation isn't smooth and isn't really around its center though I'm blitting the image360 attribute of the square in its center coordinates.

Btw if I just flip the image by 90°, it will seem to be perfectly rotating around its center.

Here is how I created my center() function :

def center(x, y, rect) :
    try:
        return (x + rect.get_width() / 2, y + rect.get_height() / 2)
    except AttributeError:
        return (x + rect.width / 2, y + rect.height / 2)

UPDATE :

Here is an example of what happens when I try to rotate the image (square case) :

rectangular image case : (I modified the GIF as I realized I had made a wrong one before)

Answer 1

Finally I solved the issue and it was related to wrong image positioning as @Tyyppi_77 has mentionned in the comments.

The blit method of pygame.Surface turns out to blit a surface in the topleft corner if coordinates are passed to the 2nd parameter.

However, if we pass a Rect object, we would be able to position the image as we want.

Here is what the documentation says :

The dest argument can either be a pair of coordinates representing the position of the upper left corner of the blit or a Rect, where the upper left corner of the rectangle will be used as the position for the blit.

And fortunately, pygame.Surface objects have a get_rect() method using which we can obtain a Rect object that can be centered at a given position.

So what I did to solve the issue is getting and updating the rotated image's rect object while positioning it to the center not to the top left corner like this :

class Square:
    def __init__(self):
        self.x, self.y, self.angle = 50, 200, 0
        self.image = load('square.png')
    
    @property
    def center360(self):
        return center(self.x, self.y, self.image)

    @property
    def image360(self):
        return pygame.transform.rotate(self.image, self.angle)

    @property
    def rect360(self):
        return self.image360.get_rect(center=self.center360)

    def blit(self):
        MyScreen.blit(self.image360, self.rect360)