检查元素是否在python列表中首次出现

my_list = [1, 2, 3, 4, 5]
element = 3

if element in my_list:
    print("Element exists in the list")
else:
    print("Element does not exist in the list")

my_list = [1, 2, 3, 4, 5]
element = 3

try:
    index = my_list.index(element)
    print("Element first appears at index", index)
except ValueError:
    print("Element does not exist in the list")

def is_first_occurrence(my_list, element):
    count = 0
    for item in my_list:
        if item == element:
            count += 1
            if count > 1:
                return False
    return True

my_list = [1, 2, 3, 4, 5]
element = 3

if is_first_occurrence(my_list, element):
    print("Element is the first occurrence in the list")
else:
    print("Element is not the first occurrence in the list")