Adding a column in pandas df using a function

In general, you can use the apply function. If your function requires only one column, you can use:

df['price'] = df['Symbol'].apply(getquotetoday)

as @EdChum suggested. If your function requires multiple columns, you can use something like:

df['new_column_name'] = df.apply(lambda x: my_function(x['value_1'], x['value_2']), axis=1)