I am trying to sort my dataframe in python pandas but the issue I am facing is that the dataframe is to be sorted on multiple columns, which is a user input. 

Basically I have stored the columns on which it is to be sorted as an array - 

```
keys=np.array(['kzip9','kzip8','kzip7','kzip6','kzip5'])

```

Then I am trying to sort as - 

```
temp_0=df.sort([keys])

```

This gives me the following error - 

> 
> ValueError: Cannot sort by duplicate column ['kzip9' 'kzip8' 'kzip7' 'kzip6' 'kzip5']
> 
> 
> 

But when I put a column name instead of 'keys' in the sort statement, it works fine.