I'm trying to add x number of blank columns to a dataframe. 

Here is my function:

```
def fill_with_bars(df, number=10):
    '''
    Add blank, empty columns to dataframe, at position 0
    '''

    numofcols = len(df.columns)

    while numofcols < number:
        whitespace = ''
        df.insert(0, whitespace, whitespace, allow_duplicates=True)
        whitespace += whitespace
    return df

```

but I get this error

```
ValueError: Wrong number of items passed 2, placement implies 1

```

I'm not sure what I'm doing wrong?