while循环中的Try/exception命令(Python)

Question

我正在尝试创建一个从给定的CT扫描目录中提取一批患者的函数。一些患者的扫描在图像分割过程中失败，所以我循环列表，直到我找到成功分割的患者的“批号”。然而，当我运行下面的代码时，它会无限循环。我不明白为什么'break‘没有终止循环。

任何想法都将不胜感激！：)

INPUT_FOLDER = "D:\CT\stage1\stage1"

patients = os.listdir(INPUT_FOLDER)
patients.sort()

#start, n_batch are given as parameters.

data = start    #initialize index for list 'validation_patients'
valid_patient_list = []   #create an empty list for patient data with successful segmentation

while True:   #iterate over variable 'data' until the list of valid patients is completed

    try:
        x = patients[data]
        load_scan(INPUT_FOLDER + '\\' + x)
        valid_patient_list.append(data)

        if len(valid_patient_list) == n_batch:  #escape while loop when the list length is equal to designated batch size

            break

        else: data += 1 #if the length of list is smaller than the desired batch number, go for the next patient

    except IndexError: 
        data += 1 # go for the next data: do not add this one to the list
        continue

#some more code below that deals with the valid_patient_list, but the loop runs infinitely..

Answer 1

如果你在patientsdata上得到一个IndexError，这是因为data >= len(patients)，一个索引超出范围的错误，所以patientsdata+1也会引发一个IndexErorr。

这会导致您的代码在引发和捕获异常之间陷入无限循环，并且代码永远不会到达“break”部分。