How to reduce multiple if statement in Python

Question

I have below code snippet:

amountLst = []
for i in range(9):
 hsv = ""
 if i == 0:
 hsv = cv2.cvtColor(barc0Img, cv2.COLOR_BGR2HSV)
 elif i == 1:
 hsv = cv2.cvtColor(barc1Img, cv2.COLOR_BGR2HSV)
 elif i == 2:
 hsv = cv2.cvtColor(barc2Img, cv2.COLOR_BGR2HSV)
 elif i == 3:
 hsv = cv2.cvtColor(barc3Img, cv2.COLOR_BGR2HSV)
 elif i == 4:
 hsv = cv2.cvtColor(barc4Img, cv2.COLOR_BGR2HSV)
 elif i == 5:
 hsv = cv2.cvtColor(barc5Img, cv2.COLOR_BGR2HSV)
 elif i == 6:
 hsv = cv2.cvtColor(barc6Img, cv2.COLOR_BGR2HSV)
 elif i == 7:
 hsv = cv2.cvtColor(barc7Img, cv2.COLOR_BGR2HSV)
 elif i == 8:
 hsv = cv2.cvtColor(barc8Img, cv2.COLOR_BGR2HSV)
 lower_bound = np.array([0, 80, 80])
 upper_bound = np.array([20, 255, 255])
 mask = cv2.inRange(hsv, lower_bound, upper_bound)
 amountLst.append(mask)

As you can see I am checking the value of i and based on it, selecting appropriate hsv. Is there a better way to do it by avoiding multiple if statement?

Answer 1

You can use a list containing the barc<int>Img:

barcImg = [
 barc0Img,
 barc1Img,
 barc2Img,
 ...
]
amountLst = []
for i in range(9):
 hsv = cv2.cvtColor(barcImg[i], cv2.COLOR_BGR2HSV)
 lower_bound = np.array([0, 80, 80])
 upper_bound = np.array([20, 255, 255])
 mask = cv2.inRange(hsv, lower_bound, upper_bound)
 amountLst.append(mask)

Answer 2

Start by putting your barcXImg references into a list:

barcImages = [barc0Img, barc1Img, barc2Img, barc3Img, barc4Img, barc5Img, barc6Img, barc7Img, barc8Img]

Calculate your upper and lower bounds just once (as they don't seem to have any dependency on anything else):

lo = np.array([0, 80, 80])
hi = np.array([20, 255, 255])

Then you can build your list with a comprehension:

amountLst = [cv2.inRange(cv2.cvtColor(img, cv2.COLOR_BGR2HSV), lo, hi) for img in barcImages]

Answer 3

I suggest you to create a function that simulates switch-case

def switch(argument):
 switcher = {
 0: cv2.cvtColor(barc0Img, cv2.COLOR_BGR2HSV),
 1: cv2.cvtColor(barc1Img, cv2.COLOR_BGR2HSV),
 2: cv2.cvtColor(barc2Img, cv2.COLOR_BGR2HSV),
 3: cv2.cvtColor(barc3Img, cv2.COLOR_BGR2HSV),
 4: cv2.cvtColor(barc4Img, cv2.COLOR_BGR2HSV),
 5: cv2.cvtColor(barc5Img, cv2.COLOR_BGR2HSV),
 6: cv2.cvtColor(barc6Img, cv2.COLOR_BGR2HSV),
 7: cv2.cvtColor(barc7Img, cv2.COLOR_BGR2HSV),
 8: cv2.cvtColor(barc8Img, cv2.COLOR_BGR2HSV),
 }
 return switcher.get(argument, "nothing")
amountLst = []
argument = yourArgument # 0,1,2,3,....
hsv = switch(argument)
lower_bound = np.array([0, 80, 80])
upper_bound = np.array([20, 255, 255])
mask = cv2.inRange(hsv, lower_bound, upper_bound)
amountLst.append(mask)