CODEWITHSUNDEEP
pythonpandaslistdataframe
Viktor Muller
Viktor Muller

Reputation: 11

Pandas - How can I get only the last element of a list to another column?

I have a Pandas dataframe that has lists in some of the columns:

email                         A                      B
[email protected]    [name1, name2]    [thing1, thing2, thing3]
[email protected]          [name]           [thing1, thing2]

I only want to have the last element of each list in each row, like this:

email                    A         B
[email protected]    name2    thing3
[email protected]      name     thing2

Is there an easy way of doing it? I initially though of something in the likes of data['newcolumn'] = data['A'][Number of row][-1], but I'm a little bit lost on hoiw doing the "number of row" part. Thanks!

Upvotes: 1

Views: 2981

Answers (4)

Sedigheh Farasat
Sedigheh Farasat

Reputation: 11

This code may help you:

data['newA']=[data['A'][i][-1] for i in range(len(data))]
data['newB']=[data['B'][i][-1] for i in range(len(data))]

Upvotes: 1

Mayank Porwal
Mayank Porwal

Reputation: 34046

You can simply use Series.str[-1]:

In [145]: df = pd.DataFrame({'email':['[email protected]', '[email protected]'], 'A':[['name1', 'name2'], ['name']], 'B':[['thing1', 'thing2', 'thing3'], ['thing1', 'thing2']]})

In [146]: df
Out[146]: 
                 email               A                         B
0  [email protected]  [name1, name2]  [thing1, thing2, thing3]
1    [email protected]          [name]          [thing1, thing2]

In [148]: df['A'] = df['A'].str[-1]

In [149]: df['B'] = df['B'].str[-1]

In [150]: df
Out[150]: 
                 email      A       B
0  [email protected]  name2  thing3
1    [email protected]   name  thing2

Upvotes: 1

uditha
uditha

Reputation: 47

Here is my answer to this, create a simple function called getLastValue() it takes your list in each row and returns the last value of that list. see below.

import pandas as pd

data = {
    'email' : ['[email protected] ', '[email protected]'],
    'A': [['name1','name2'], ['name']],
    'B': [['thing1', 'thing2', 'thing3'], ['thing1', 'thing2']]
}

def getLastValue(aList):
    return aList[-1]

df = pd.DataFrame(data)

df['A'] = df['A'].apply(getLastValue)
df['B'] = df['B'].apply(getLastValue)

print(df)

Upvotes: 1

oskros
oskros

Reputation: 3285

Assuming your dataframe is called df, you could do something like the following

def return_last_element(row):
    # If the row of the given column is list or a tuple, get the last element
    if isinstance(row, (list, tuple)):
        return row[-1]

    # Otherwise just return the value
    else:
        return row

# Loop over all columns, and apply the function to each row of each column
for col in df.columns:
    df[col] = df[col].apply(return_last_element)

Upvotes: 1

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