Accessing the first elements in a array of Lists (Python)

Question

I have a large dataframe df_c with a column type_info1 each rows contains a list with two elements .

I need to access the first element of each list on the array object. Is there a quick way to do it directly on the dataframe without going through the for loop etc or maybe use numpy :

df_c.loc[:,'type_info1'].values

results :

array([list(['AB#5', 'XYZ/ABCD']), list(['TB#5', 'XYZ/ABCD']),
       list(['CD#5', 'XYZ/ABCD']), ..., list(['BF#5', 'XYZ/ABCD']),
       list(['GH#7', 'XYZ/ABCD']), list(['FL#5', 'XYZ/ABCD'])],
      dtype=object)

any suggestion is welcome. thank you

gmds · Accepted Answer · 2019-03-05 12:43:58Z

1

Use an accessor: df_c['type_info1'].str[0]

answered Mar 5, 2019 at 12:43

gmds

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John Sloper · Accepted Answer · 2019-03-05 20:18:13Z

1

You could use list comprehension for this:

[item[0] for item in df_c.loc[:,'type_info1'].values]

or perhaps zip:

list(zip(*df_c.loc[:,'type_info1'].values))[0]

Both of these assume that none of the lists are empty btw.

If some are empty and you could e.g. skip those in the list comprehension:

[item[0] for item in df_c.loc[:,'type_info1'].values if item]

edited Mar 5, 2019 at 20:18

answered Mar 5, 2019 at 12:37

John Sloper

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