Why does the length of the elements in the list shrink?

My test code:

num = ['a',
       'b',
       'c',
       'd',
       'e'
       'f']
num_len = len(num)
print(num_len)

The output is 5, but I think it should be 6, why?

>Solution :

As well as what other people have answers, print the list so you can see what Python sees in the list:

>>> print(num)
['a', 'b', 'c', 'd', 'ef']

then you can see where the problem is.