小编Mar*_*ria的帖子

我已经使用 python 几年了，从未见过is关键字在 if 条件下用作函数。我遇到了这段代码。它按预期工作，但我不知道 is() 的作用。

def face_ext(img):
    gray = frame
    faces = face_cascade.detectMultiScale(gray, scaleFactor=1.5, minNeighbors=5)

    if faces is():
        return None

    for(x, y, w, h) in faces:
        cropped_face = img[y:y+h, x:x+w]

    return cropped_face

删除is()代码时会产生以下错误：

[INFO] Initializing face capture. Look the camera and wait ...
Traceback (most recent call last):
  File "c:\Users\smoke\miniconda3\envs\skyhawk\Scripts\skyhawk-script.py", line 33, in <module>
    sys.exit(load_entry_point('skyhawk', 'console_scripts', 'skyhawk')())
  File "c:\Users\smoke\miniconda3\envs\skyhawk\lib\site-packages\click\core.py", line 829, in __call__
    return self.main(*args, **kwargs)
  File "c:\Users\smoke\miniconda3\envs\skyhawk\lib\site-packages\click\core.py", line 782, in main
    rv = …