Question

这是整个模块。所有的＆＃34; elif＆＃34;语句是有效的语法，如果改为＆＃34;如果＆＃34;语句

def processRGB(item, matrix):
    threshhold = 229
    red, green, blue = matrix[0, 0]
    if red <= threshhold and green <= threshhold and blue <= threshhold:
        picture, boundary = RGBUpright(item, matrix, 0)
    red, green, blue = matrix[item[0].size[0] - 1, 0]
    elif red <= threshhold and green <= threshhold and blue <= threshhold:
        picture, boundary = RGBUpright(item, matrix, 90)
    red, green, blue = matrix[0, item[0].size[1] - 1]
    elif red <= threshhold and green <= threshhold and blue <= threshhold:
        picture, boundary = RGBUpright(item, matrix, 180)
    red, green, blue = matrix[item[0].size[0] - 1, item[0].size[1] - 1]
    elif red <= threshhold and green <= threshhold and blue <= threshhold:
        picture, boundary = RGBUpright(item, matrix, 270)
    final = picture[0].crop(boundary)
    final.load()
    return final

Answer 1

在python中，if语句会在缩进更改后立即结束。如果没有前一个elif，你就不能拥有if。我猜你希望你的代码看起来像这样，因为缩进的不同，这是有效的语法。

def processRGB(item, matrix):
    threshhold = 229
    red, green, blue = matrix[0, 0]
    if red <= threshhold and green <= threshhold and blue <= threshhold:
        picture, boundary = RGBUpright(item, matrix, 0)
        red, green, blue = matrix[item[0].size[0] - 1, 0]
    elif red <= threshhold and green <= threshhold and blue <= threshhold:
        picture, boundary = RGBUpright(item, matrix, 90)
        red, green, blue = matrix[0, item[0].size[1] - 1]
    elif red <= threshhold and green <= threshhold and blue <= threshhold:
        picture, boundary = RGBUpright(item, matrix, 180)
        red, green, blue = matrix[item[0].size[0] - 1, item[0].size[1] - 1]
    elif red <= threshhold and green <= threshhold and blue <= threshhold:
        picture, boundary = RGBUpright(item, matrix, 270)
    final = picture[0].crop(boundary)
    final.load()
    return final

Answer 2

如果前一个elif语句为真，那么if行之前的语句应该缩进到与它们之前的行相同的级别。否则，elif应该是if，因为您正在访问另一个代码块。

Answer 3

这是因为：

if red <= threshhold and green <= threshhold and blue <= threshhold:
    picture, boundary = RGBUpright(item, matrix, 0)

上面的内容如果在此结束，因为范围是由缩进定义的。

red, green, blue = matrix[item[0].size[0] - 1, 0]

因为“if”和“elif”语句之间有一些代码。 “elif”与上述“if”无关，我们不能将“elif”指定为独立声明。它应该与“if”或其他“elif”语句相关联，这不是在这种情况下。

elif red <= threshhold and green <= threshhold and blue <= threshhold:
    picture, boundary = RGBUpright(item, matrix, 90)

与其他“elif”相同的解释。

如果不清楚，请告诉我。

在Python 2.7.5中，为什么＆＃34; if（code）＆＃34;有效的语法，但＆＃34; elif（相同的代码）＆＃34; ISN＆＃39; T'

3 个答案: