正如你在问题中提到的。
您不需要将input()转换为int

student_id = int(input("Enter Student ID (8-digit number): "))

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你留着吧：

student_id = input("Enter Student ID (8-digit number): ")

型
默认情况下，input()的数据类型为string。

student_id = input("Enter Student ID (8-digit number): ")
if len(student_id) != 8:
    print("The student ID number you have entered is invalid, please enter an 8-digit number")

型

if len(str(student_id)) != 8:
    print("The student ID number you have entered is invalid, please enter an 8-digit number")

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如果你想继续要求用户输入一个合适的学生ID，你可以这样做：

student_id = int(input("Enter Student ID (8-digit number): "))

while len(str(student_id)) != 8:
    print("The student ID number you have entered is invalid, please enter an 8-digit number")

    student_id = int(input("Enter Student ID (8-digit number): "))

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但是请记住，如果用户将int()函数无法使用的任何内容传递到输入，则此代码将抛出错误。

下面是使用Regex的另一种方法：

while True:
        student_id = int(input("Enter Student ID (8-digit number): "))
        pattern = re.compile("^[0-9]{8}$")
        check_id = pattern.search(str(student_id))
        if check_id:
            print("The student ID number you have entered is valid. Thank you!")
            break
        else:
            print("The student ID number you have entered is invalid, please enter an 8-digit number")

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注意：作为提醒，您将需要import re