def replace_comma_by_point(file):
    """
    replaces all commas by point in a file (do that inplace)

    @param      file        file to process
    """
    with open(file, 'r') as f:
        text = f.read()
    text = text.replace(',', '.')
    with open(file, 'w') as f:
        f.write(text)
