Filtering a column of lists of strings in a Pandas DataFrame

Question

df=pd.DataFrame({'sym':['A', 'B', 'C', 'D'],'event':[['1','2', '3'], ['1'], ['2', '3'],['2']]} )

df

    sym event
0   A   [1, 2, 3]
1   B   [1]
2   C   [2, 3]
3   D   [2]

Event column is made up of lists of strings. I am trying to filter the event column for any rows that contain '3' so I am looking for index 0 and 2.

I know to use

["3" in df.event[0]]

for each row and I think a lambda function would push me over the finish line.

df[df.event.astype(str).str.contains('3')]? Or whats your desired output? — wwnde
– wwnde, Commented Feb 8, 2021 at 2:56

wwnde · Accepted Answer · 2021-02-08 03:18:42Z

4

Please try:

print(df[df.event.astype(str).str.contains(r'\b3\b')])



sym      event
0   A  [1, 2, 3]
2   C     [2, 3]

edited Feb 8, 2021 at 3:18

answered Feb 8, 2021 at 3:06

wwnde

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2 Comments

BENY Over a year ago

this will filter the '33' as well ~

wwnde Over a year ago

Thanks, edited to ensure only 3 is picked

Ferris · Accepted Answer · 2021-02-08 03:12:26Z

3

Series.explode to split list-like values to rows

use explode to turn a list to row:

'3' in df['event'].explode().values

to find which row contains '3', use index:

idx = df['event'].explode() == '3'
df.loc[idx[idx].index]

edited Feb 8, 2021 at 3:12

answered Feb 8, 2021 at 2:57

Ferris

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3 Comments

wlbsr Over a year ago

thanks. so how would I filter the df rows rows where df['event'] contains "3"?

Ferris Over a year ago

you can use the row's index. as explode keep the row's origin index.

anky Over a year ago

you can also do: df['event'].explode().eq('3').any(level=0) with explode . Adding an alternative :)

BENY · Accepted Answer · 2021-02-08 03:15:12Z

2

Let us try

out = df[pd.DataFrame(df.event.tolist()).isin(['3']).any(1).values]
Out[78]: 
  sym      event
0   A  [1, 2, 3]
2   C     [2, 3]

answered Feb 8, 2021 at 3:15

BENY

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