night_day.py

from sklearn import linear_model

Y = np.array(Y) # array of training answers, 1 or 0

X = np.array([]) # array of image brightness
for filename in filenames:
    # load the images
    image = misc.imread(constants.IMAGE_64_PATH + '/' + filename, mode='L')
    avg_brightness = np.matrix(image).mean()
    X = np.append(X, avg_brightness)
X = np.array([X]).transpose()

clf = linear_model.LogisticRegression(C=1e5)
clf.fit(X, Y)