how can rectify error from the below code

[wavic]

Hello! You pass to getingc1() "domain ontologies" as an argument. Print c1  before the return statement to see what is going out. You get a single list with a single value ' domain'.

In [9]: mystr = ['domain', 'ontologies']

In [10]: c1 = []

In [11]: for i in mystr[:1]:
    ...:     c1.append(i)
    ...:     

In [12]: c1
Out[12]: ['domain']

So in frequency1() you count for a string which is not in 'd'.

In [20]: print(termslist)

dict_items([])

 
So you get an empty container from which you return 'v'. In the end the returned value from frequency1 function is None. You can't divide None with something else.