这是源代码

my_name = "Ella"

my_age = 18

your_name = input("what is your name?")

your_age = input("how old are you?")

print ("my name is",my_name,",and i am",my_age,"years old.")

print ("your name is",your_name,",and you are",your_age,".")

print ("thank you for buying my book,",your_name,"!")

下面是错误提示，完全不懂原因是什么？求解

=================== RESTART: D:\Python\PY file\thankyou.py ===================

what is your name?ella

Traceback (most recent call last):

  File "D:\Python\PY file\thankyou.py", line 3, in <module>

    your_name = input("what is your name?")

  File "<string>", line 1, in <module>

NameError: name 'ella' is not defined

>>>