All libraries have driver code, you can look up the docs to find it

i'm assuming you're using python and also the inbuilt 'permutations' function of the itertools module

the name of the function is also 'permutations', so when you call permutations(...), while you think it calls the itertools 'permutations', the function calls itself

Of course, how do you think the library works?

I'm having trouble understanding how the first test returns 37 for M. I am only getting 100. Thanks in advance

In line number 6, You should return true, If it ain't, it will print false for isogram words also