Question

我正打算打印出找到的素数。我想添加到prime []，但我得到一个TypeError

line 63, in isprime
    primes += n
TypeError: 'int' object is not iterable

代码：

def isprime(n):
    primes = []
    if n == 1:
        print '1 is special'
        return False
    for x in range(2, n):
        if n%x == 0:
            print '{} equals {} x {}'.format(n, x, n // x)
            return False
    else:
        primes += n
        print (n, "is a prime number")
        return True

for n in range(1, 1000):
    isprime(n)

Answer 1

+=上的

list旨在将list连接到另一个list。如果你想在primes.append(n)的末尾添加一个元素，你可以直接做到：

list

或制作一个临时.append以允许列表连接操作工作（这种方法较慢，并且只是更简洁，涉及更大的内存流失;我强烈建议使用+=除非你需要要一次添加多个元素，在这种情况下，primes += [n]方法可以更好地扩展多元素列表文字）：

    func sFunc_imageFixOrientation(img:UIImage) -> UIImage {

        // We need to calculate the proper transformation to make the image upright.
        // We do it in 2 steps: Rotate if Left/Right/Down, and then flip if Mirrored.
        var transform:CGAffineTransform = CGAffineTransformIdentity
        // Rotate image clockwise by 90 degree
        if (img.imageOrientation == UIImageOrientation.Up) {
            transform = CGAffineTransformTranslate(transform, 0, img.size.height);
            transform = CGAffineTransformRotate(transform,  CGFloat(-M_PI_2));
        }

        if (img.imageOrientation == UIImageOrientation.Down
            || img.imageOrientation == UIImageOrientation.DownMirrored) {

            transform = CGAffineTransformTranslate(transform, img.size.width, img.size.height)
            transform = CGAffineTransformRotate(transform, CGFloat(M_PI))
        }

        if (img.imageOrientation == UIImageOrientation.Left
            || img.imageOrientation == UIImageOrientation.LeftMirrored) {

            transform = CGAffineTransformTranslate(transform, img.size.width, 0)
            transform = CGAffineTransformRotate(transform, CGFloat(M_PI_2))
        }

        if (img.imageOrientation == UIImageOrientation.Right
            || img.imageOrientation == UIImageOrientation.RightMirrored) {

            transform = CGAffineTransformTranslate(transform, 0, img.size.height);
            transform = CGAffineTransformRotate(transform,  CGFloat(-M_PI_2));
        }

        if (img.imageOrientation == UIImageOrientation.UpMirrored
            || img.imageOrientation == UIImageOrientation.DownMirrored) {

            transform = CGAffineTransformTranslate(transform, img.size.width, 0)
            transform = CGAffineTransformScale(transform, -1, 1)
        }

        if (img.imageOrientation == UIImageOrientation.LeftMirrored
            || img.imageOrientation == UIImageOrientation.RightMirrored) {

            transform = CGAffineTransformTranslate(transform, img.size.height, 0);
            transform = CGAffineTransformScale(transform, -1, 1);
        }


        // Now we draw the underlying CGImage into a new context, applying the transform
        // calculated above.
        let ctx:CGContextRef = CGBitmapContextCreate(nil, Int(img.size.width), Int(img.size.height),
                                                     CGImageGetBitsPerComponent(img.CGImage), 0,
                                                     CGImageGetColorSpace(img.CGImage),
                                                     CGImageGetBitmapInfo(img.CGImage).rawValue)!;
        CGContextConcatCTM(ctx, transform)


        if (img.imageOrientation == UIImageOrientation.Left
            || img.imageOrientation == UIImageOrientation.LeftMirrored
            || img.imageOrientation == UIImageOrientation.Right
            || img.imageOrientation == UIImageOrientation.RightMirrored
            || img.imageOrientation == UIImageOrientation.Up
            ) {

            CGContextDrawImage(ctx, CGRectMake(0,0,img.size.height,img.size.width), img.CGImage)
        } else {
            CGContextDrawImage(ctx, CGRectMake(0,0,img.size.width,img.size.height), img.CGImage)
        }


        // And now we just create a new UIImage from the drawing context
        let cgimg:CGImageRef = CGBitmapContextCreateImage(ctx)!
        let imgEnd:UIImage = UIImage(CGImage: cgimg)

        return imgEnd
    }
}

Answer 2

primes是一个列表，因此要向其添加n int，您必须使用append方法。将primes += n替换为primes.append(n)。

为什么我不能在一个素数列表中添加一个找到的素数？

2 个答案: