Pandas add columns error must be same length as key?-CodePudding

I got this error when I try to split one column and create additional columns in current dataframe:

Columns must be same length as key

if 'FULLNAME' in dataset.columns:
       dataset[['FIRSTNAME','LASTNAME']] = dataset.FULLNAME.str.split(" ", 1)

Before I set static columns names:

dataset.columns = ["NUM", "MMYY", "AGE", "FULLNAME", "ADDRESS", "CITY", "STATE", "ZIP", "COUNTRY", "PHONE"]

How to fit it?

I suppose some of columns has not FULLNAME to extract

May be to use this:

dataset["FIRSTNAME"] = None
dataset["LASTNAME"] = None

if 'FULLNAME' in dataset.columns:
    r = dataset.FULLNAME.str.split(" ", 1)
    if (r[0]):
        dataset["LASTNAME"] = r[0]
    if (r[1]):
        dataset["FIRSTNAME"] = r[1]

Dataset is:

"NUM", "MMYY", "AGE", "FULLNAME", "ADDRESS", "CITY", "STATE", "ZIP", "COUNTRY", "PHONE"

1 1010 18 OLEG Kirova Wage US 1911 US  9584345345
2 1011 19 Krina Kirova Wage US 1911 US  9584345345
3 1012 20 Marina Kirova Wage US 1911 US  9584345345

CodePudding user response：

I think you want to pass expand=True into split so that it returns a DataFrame...

if 'FULLNAME' in dataset.columns:
       dataset[['FIRSTNAME','LASTNAME']] = dataset.FULLNAME.str.split(" ", 1, expand=True)

CodePudding user response：

Assuming you have data like this:

import pandas as pd
dataset = pd.DataFrame({"FULLNAME": ["John Smith", "Jane Smith", "Joe Bloggs"]})

Your problem is that

dataset.FULLNAME.str.split(" ", 1)

only produces one column.

print(dataset.FULLNAME.str.split().shape)
(3,)

The doc for split shows that you probably want expand=True.

Here's a MWE...

import pandas as pd
dataset = pd.DataFrame({"FULLNAME": ["John Smith", "Jane Smith", "Joe Bloggs"]})

if 'FULLNAME' in dataset.columns:
    dataset[['FIRSTNAME','LASTNAME']] = dataset.FULLNAME.str.split(expand=True)