I have a pandas dataframe, which contains some pretty infiltered data

```
df['Q53']
OUTPUT:
0      Hvor mange timer træner din virksomhed medarbe...
3                                                    NaN
4                                                    NaN
5                                                    NaN
6                                                      2
7                                                    NaN
8                                                     10
9                                                    NaN
10                                                    50
11                                                   NaN
12                                                     ?
13                                                     ?
14                                                     8
15                                                   NaN
16                                                     2
17                                                     0
18                                                     1
19                                                     1
20                                                     5
21                                             7x3 timer
22                                                   NaN
23                                               8 timer
24                                                   NaN
25                                                     0
26                                                     8
27                                                   NaN

```

the issue now, is that i want to just have the integers left in the column, and then cast them as a float, so i can do some data visualization with the column. 

I was wondering if i could do some standardized filtering, but i could not get get it to work.

Is there an operation, where i can filter out all `NaN` and `String` values, and just be left with a value, that could be casted into a `float` or `int`