Alternate options to combine rows data without "For Loop & If else" in python

Question

I have to combine the rows based on the last word in the row, Like

data is in below format

Answer:

Should combine like below

I have written the below code & it's working fine as expected, however, it becomes very slow when I have huge data (10K+ rows).

#split the string & take the last word

df["last_Word"] = df["Donor"].str.split().str[-1].str.lower()
df["Match_end"] = df["last_Word"].isin(align["KeyWords_end"].str.lower())

Add two new columns in a data frame

df["Cleaned"]= ""
df["Mark"]= ""

Align the text based on the last word & mark delete rows as "delete"

for i in range(len(df)):
    if ((df["Match_end"].iloc[i]== True) and (df["Match_end"].iloc[i+1]== True)):
        df["Mark"].iloc[i+1]= "delete"
        df["Mark"].iloc[i+2]= "delete"
        df["Cleaned"].iloc[i]= df["Donor"].iloc[i] + " " +df["Donor"].iloc[i+1]+ " " +df["Donor"].iloc[i+2]

Delete the mark rows

df = df[~df['Mark'].str.contains("delete")]

Update the newly created column

for i in range(len(df)):
    if len(df["Cleaned"].iloc[i])== 0:
    df["Cleaned"].iloc[i]= df["Donor"].iloc[i]

#Drop the unwanted columns

df.drop(["Donor","Mark","last_Word","Match_end"], axis = 1, inplace = True)

#Rename the newly created column

df.rename(columns= {"Cleaned": "Donor"},inplace = True)

Answer 1

Assuming you want to combine the strings ending in "and" or "&", use a regex to identify those strings, then groupby.agg :

m = ~df['donor'].str.contains(r'(?:\band|&)\s*$').shift(fill_value=False)

df.groupby(m.cumsum(), as_index=False).agg({'donor': ' '.join})

Example output:

                      donor
0            ABC, DEF & GHI
1  JKL MNO and  PQR and STU

Used input:

          donor
0    ABC, DEF &
1           GHI
2  JKL MNO and 
3       PQR and
4           STU