Pandas Dataframe Check if column value is in column list

Question

I have a dataframe df:

data = {\'id\':[12,112],
        \'idlist\':[[1,5,7,12,112],[5,7,12,111,113]]
       }
df=pd.DataFrame.from_dict(data)
         


        

Answer 1

Try simple for loop:

flaglist = []
for i in range(len(df)):
    if df.id[i] in df.idlist[i]:
        flaglist.append(1)
    else:
        flaglist.append(0)
df["flag"] = flaglist 

df:

    id                idlist  flag
0   12    [1, 5, 7, 12, 112]     1
1  112  [5, 7, 12, 111, 113]     0

To drop rows:

flaglist = []
for i in range(len(df)):
    if df.id[i] not in df.idlist[i]:
        flaglist.append(i)
df = df.drop(flaglist)

df:

   id              idlist  flag
0  12  [1, 5, 7, 12, 112]     1

Above can be converted to list comprehension for creating a flag column:

df["flag"] = [df.id[i] in df.idlist[i]    for i in range(len(df))]
print(df)
#     id                idlist   flag
# 0   12    [1, 5, 7, 12, 112]   True
# 1  112  [5, 7, 12, 111, 113]  False

or

df["flag"] = [1 if df.id[i] in df.idlist[i] else 0    for i in range(len(df))]
print(df)
#     id                idlist  flag
# 0   12    [1, 5, 7, 12, 112]     1
# 1  112  [5, 7, 12, 111, 113]     0

and for selecting out rows:

flaglist = [i   for i in range(len(df))   if df.id[i] in df.idlist[i]]
print(df.iloc[flaglist])
#    id              idlist
# 0  12  [1, 5, 7, 12, 112]