How to check that each list in a list of list is the same length

Question

I have a list and a list of list

A=["grp 1", "grp 2"]
B=[["1","2"],["3","4"],["5","6"]]

how do I check that each list in B is equal to the length of A?

I would like something like

if len(A) != len(list in B):
     raise ValueError('special error message')

Answer 1

If you want to make sure that every single element of B is not equal to the length of A then you can use:

a_len = len(A)
all(len(x) != a_len for x in B)

Alternatively you can use the following if you want to see if any element of B is not the same length as A :

a_len = len(A)
any(len(x) != a_len for x in B)

So in your case you could use:

a_len = len(A)
if any(len(x) != a_len for x in B):
    raise error

Answer 2

as additional note, if you want to know if every element in the list have the same length regardless of its value, you can use

len( set( len(x) for x in my_list ) ) == 1 

with set you eliminate all duplicates so if in the end if its length is more than one then some stuff there have different size