I have the following df, and I would like to apply a filter over the column names and simply remain those that begin with a certain string:

This is my current df:

```
ruta2:
             Current SAN Prev.1m SAN Prev.2m SAN Prev.3m SAN Current TRE  \

A                   5           6           7           6           3
B                   6           5           7           6           6
C                  12          11          11          11           8

```

Basically what I would like is to filter the dataframe and remain the columns that begin with `Current`. 

Then the desired output would be: 

```
ruta2:
             Current SAN  Current TRE  

A                   5            3
B                   6            6
C                  12            8

```

In order to do this I tried this filter but outputs a value error :

```
ruta2=ruta2[~(ruta2.columns.str[:4].str.startswith('Prev'))]

```