def df_stdev(row, column_label_list=None):
    """
	Calculate the standard deviation of each row for the specified columns of a data frame

	Do not call this function directly; use it with df.apply() instead.

	data_frame["Stdev"] = data_frame.apply(df_stdev, args=(
				["Bob", "Alice"],), axis=1)

	:param row: row of the data frame
	:type row: pandas.core.series.Series
	:param column_label_list: list of column labels to calculate standard deviation for
	:type column_label_list: list

	:return: Standard deviation
	:rtype: float
	"""
    from numpy import nanstd
    if column_label_list is None:
        column_label_list = list(row.index)
    return nanstd(row[column_label_list])
