如果您只是想检查它是否包含重复项.一旦该函数找到出现多次的元素，它就会作为重复项返回.

If you simply want to check if it contains duplicates. Once the function finds an element that occurs more than once, it returns as a duplicate.

my_list = [1, 2, 2, 3, 4]

def check_list(arg):
    for i in arg:
        if arg.count(i) > 1:
            return 'Duplicate'

print check_list(my_list) == 'Duplicate' # prints True