string split with expand=True. Can anyone explain what is the meaning?

Question

all_data['Title']= all_data['Name'].str.split(', ', expand=True)[1].str.split('.', expand=True)[0]

Can anyone explain what is the meaning of this line of code? Especially with the expand=True and [1] [0].

That isn't the usual string split method, it's a specific method of whatever kind of object `all_data['Name'].str` returns. I believe you're working with a Pandas dataframe here, you need to see the Pandas documentation to see what methods its objects define, and what parameters they take. — jasonharper, Sep 08 '20 at 14:59

score 7 · Answer 1 · answered May 11 '22 at 01:13

If you are using Pandas it is likely that you know also Jupyter Notebooks. So, for simplicity and readability let's complete the code you've posted with some additional information in a Notebook-like format:

(this markdown is here to override an error in the answer window interpreter)

```lang-python
    import pandas as pd
    
    raw_name = ['Bob, Mr. Ross', 'Alice, Mrs. Algae', 'Larry, Mr. lemon', 'John, Mr. Johnson']
    all_data = pd.DataFrame({'Name': raw_name})
    
    # This the OP's line
    all_data['Title'] = all_data['Name'].str.split(', ', expand=True)[1].str.split('.', expand=True)[0]
    
    all_data

	Name	Title
0	Bob, Mr. Ross	Mr
1	Alice, Mrs. Algae	Mrs
2	Larry, Mr. Lemon	Mr
3	John, Mr. Johnson	Mr

Where the expand=True renders a set of columns of strings. Therefore, after the first split, you may apply again another str.split method since the first split has rendered dataframe of strings as columns. This would have been a little more complicated with a regular split (or expand=False) which renders a series of lists.

Better explained with code examples:

    all_data['Name'].str.split(', ', expand=False) # or no expand at all

	0
0	[Bob, Mr. Ross]
1	[Alice, Mrs. Algae]
2	[Larry, Mr. Lemon]
3	[John, Mr. Johnson]

    all_data['Name'].str.split(', ', expand=True)

	0	1
0	Bob	Mr. Ross
1	Alice	Mrs. Algae
2	Larry	Mr. Lemon
3	John	Mr. Johnson

    all_data['Name'].str.split(', ', expand=True)[1].str.split('.', expand=False)

	0
0	[Mr, Ross]
1	[Mrs, Algae]
2	[Mr, Lemon]
3	[Mr, Johnson]

    all_data['Name'].str.split(', ', expand=True)[1].str.split('.', expand=True)

	0	1
0	Mr	Ross
1	Mrs	Algae
2	Mr	Lemon
3	Mr	Johnson

Reference: https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.str.split.html

The error that keeps popping up is: "Your post appears to contain code that is not properly formatted as code. Please indent all code by 4 spaces using the code toolbar button or the CTRL+K keyboard shortcut. For more editing help, click the [?] toolbar icon." — Alejandro QA, May 11 '22 at 01:14

score 2 · Answer 2 · answered Sep 08 '20 at 17:35

Take a look here: pandas.Series.str.split

Expand the split strings into separate columns.

If True, return DataFrame/MultiIndex expanding dimensionality.

If False, return Series/Index, containing lists of strings.

s = pd.Series(
    [
        "this is a regular sentence",
    ]
)    
s.str.split(expand=True)

0 1 2 3 4
this is a regular sentence

string split with expand=True. Can anyone explain what is the meaning?

2 Answers2