How to select a specific element from a list of rows in python

Question

I have the following series (df):

Index    Information
1        [2, A, C]
2        [3, B, C]
3        [4, C, H]
4        [5, D, H]
5        [6, E, H]
6        [7, F, H]

and I want a series that only extracts and stores the third value of each list :

Index    Information
1        [C]
2        [C]
3        [H]
4        [H]
5        [H]
6        [H]

If I try df[0][2], it correctly gives the required output [C].

however, if I try df[:][2], instead of giving

[C]
[C]
[H]
[H]
[H]
[H]

the output is

3        [4, C, H]

What should be the correct syntax for this?

how are you creating the dataframe?

bluesmonk
– bluesmonk

2018-05-21 17:16:03 +00:00
Commented May 21, 2018 at 17:16 — bluesmonk
– bluesmonk, Commented May 21, 2018 at 17:16

piRSquared · Accepted Answer · 2018-05-21 17:56:21Z

2

`pandas.Series.str`

df.Information.str[2:3]

0    [C]
1    [C]
2    [H]
3    [H]
4    [H]
5    [H]
Name: Information, dtype: object

With `assign`

df.assign(Information=df.Information.str[2:3])

   Index Information
0      1         [C]
1      2         [C]
2      3         [H]
3      4         [H]
4      5         [H]
5      6         [H]

comprehension per @coldspeed

df.assign(Information=[l[2:3] for l in df.Information.tolist()])

   Index Information
0      1         [C]
1      2         [C]
2      3         [H]
3      4         [H]
4      5         [H]
5      6         [H]

edited May 21, 2018 at 17:56

answered May 21, 2018 at 17:12

piRSquared

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3 Comments

cs95 Over a year ago

You may go for the alternative [l[2:3] for l in df.Information.tolist()] as well.

kdba Over a year ago

what if the name of the column labelled 'information' is a varies depending on size of the data? How can I represent it?

harpan Over a year ago

@KrishnaAnapindi In that case [l[-1:] for l in df.Information.tolist()] would do the trick.

Toby Petty · Accepted Answer · 2018-05-21 17:14:26Z

0

Another alternative:

df["new_col"] = df["Information"].apply(lambda x: x[2])

answered May 21, 2018 at 17:14

Toby Petty

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How to select a specific element from a list of rows in python

2 Answers 2

`pandas.Series.str`

With `assign`

comprehension per @coldspeed

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2 Answers 2

pandas.Series.str

With assign

comprehension per @coldspeed

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`pandas.Series.str`

With `assign`