在字符串列表中寻找字符串，并在pandas中创建新列

Question

I am new to Python and trying to solve the performance issue here. I have 2 data frames

Dataframe 1

col1        col2
holiday     party
party       party
bagel       snack
fruit       snack

Data Frame 2:

col1                            col2
bagel wednesday                 snack               
coffee for party                snack
holiday party                   party

Data Frame 1 has 2 columns. I need to lookup DataFrame1.col1, in DataFrame2.col1 and create a new column in DataFrame2.col2 with DataFrame1.col2 value Currently, I am achieving this using a loop and it is taking a very long time. I am looking for an efficient way to do this. Also, if I get multiple matches I should always go with the first match found from DataFrame1. For example, "coffee for party" has 2 matches from DF1, snack and party, in which case "snack" should be picked from DF1.col2.

Thanks RL

Answer 1

I think you have to loop over the days of the week (but not all the rows of df2 (well, df.col.str.contains will do the inner loop for you in an optimized manner)).

for item in df1.col2.unique():
    for idx, row in df1[df1.col2==item].iterrows():
        df2.loc[df2.col1.str.contains(row.col1), 'col3'] = item