[FIXED] Why does the type error appear if the column is clear?

Issue

I checked w_table.iloc[i,4] and didn't find NoneType objects in it. What's the matter could it be?

check = ['word']
for i in range(len(w_table)):
    if w_table.iloc[i, 4] != 'Null':
        if w_table.iloc[i, 4] in check:
            w_table = w_table.drop(w_table.index[i])
        else:
            check = check.append(w_table.iloc[i, 4])
        w_table.index = np.arange(len(w_table)) 

After executing above code I am getting following TypeError

 TypeError                                 Traceback (most recent call
 last) <ipython-input-74-40b9156195fa> in <module>()

       2 for i in range(len(w_table)):
       3     if w_table.iloc[i, 4] != 'Null':
       4         if w_table.iloc[i, 4] in check:
       5             w_table = w_table.drop(w_table.index[i])
       6         else:

 TypeError: argument of type 'NoneType' is not iterable

Solution

The problem is with this line:

check = check.append(w_table.iloc[i, 4])

list.append is an in-place operation and returns None. Instead, just use:

check.append(w_table.iloc[i, 4])

For better performance, use set and set.add:

check = {'word'}
...
check.add(w_table.iloc[i, 4])

Even better, you can use vectorised functionality to avoid loops altogether. For this, you should provide a complete example, probably in a separate question.

Answered By - jpp