Converting nested dict into a single unchanging unique number

I’m working on a minimax algorithm project and I am trying to find a way to save board values in a text file so they don’t need to be calculated over and over again each time the program is tested. I have the board stored as a nested dictionary.

rows = {
    4:{1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0},
    3:{1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0},
    2:{1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0},
    1:{1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0},
    }

I tried doing this, which gives the desired result but is not at all optimized and I’m sure there is a way to do this better.

 rows = {
    4:{1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0},
    3:{1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0},
    2:{1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0},
    1:{1:0,2:0,3:0,4:0,5:0,6:0,7:0,8:0},
    }

e = []
for key in rows:
    e.append(list(rows[key].values()))
e=str(e)
e=e.replace ("[",""); e=e.replace ("]","")
e=e.replace (" ","")
e=e.replace (",","")
print(e)