python - 全局找不到名称代码错误

Question

def choose():
  file = pickAFile()
  pic = makePicture(file)
  return pic

def negative(pic):
  for p in getPixels(pic):
    setRed(p, 255 - getRed(p))
    setGreen(p, 255 - getGreen(p))
    setBlue(p, 255 - getBlue(p))
  explore(pic)

def main():
  choose()
  negative(pic)

我收到这个错误:

The error was:pic Name not found globally. A local or global name could not be found. You need to define the function or variable before you try to use it in any way. Please check line 15 of C:\Users\nh_2109\Desktop\s

求助？:D

Answer 1

您还没有在 main 方法中定义 pic。

def main():
   pic = choose()
   negative(pic)

可能是您想要的，因为 choose() 返回一个 Pic 类的实例。