str.split() for splitting in Pandas

Introduction

We use str.split() to break text into smaller parts. This helps us work with each piece separately.

You have a column of full names and want to separate first and last names.

You want to split a list of tags stored as one string into individual tags.

You need to extract parts of an address stored in one column.

You want to convert a string of numbers separated by commas into separate columns.

Syntax

Pandas

Series.str.split(pat=None, n=-1, expand=False)

pat is the character or pattern to split on. If None, splits on whitespace.

n limits the number of splits. Default -1 means no limit.

expand=True returns a DataFrame with split parts as columns.

Examples

Splits on whitespace by default.

Pandas

df['col'].str.split()

Splits the string at each comma.

Pandas

df['col'].str.split(',')

Splits only once at the first dash.

Pandas

df['col'].str.split('-', n=1)

Splits on commas and returns a DataFrame with each part as a separate column.

Pandas

df['col'].str.split(',', expand=True)

Sample Program

This code splits the full_name column into two columns: first_name and last_name.

Pandas

import pandas as pd

data = {'full_name': ['Alice Smith', 'Bob Johnson', 'Charlie Lee']}
df = pd.DataFrame(data)

# Split full_name into first and last name
split_names = df['full_name'].str.split(' ', expand=True)
split_names.columns = ['first_name', 'last_name']

print(split_names)

Important Notes

If you use expand=False (default), the result is a Series of lists.

Use expand=True to get a DataFrame with separate columns for each split part.

If the number of splits varies, some columns may have missing values (NaN).

Summary

str.split() breaks text into parts based on a separator.

Use expand=True to get multiple columns from one text column.

This helps analyze or clean text data by working with smaller pieces.

Practice

1. What does the str.split() method do in pandas when applied to a text column?

easy

A. It breaks the text into parts based on a separator.

B. It merges multiple columns into one string.

C. It converts numbers to strings.

D. It removes all spaces from the text.

Solution

1. Step 1: Understand the purpose of str.split()

   The method splits strings into parts using a separator, like spaces or commas.

2. Step 2: Compare with other options

   Options A, B, and C describe different string operations, not splitting.

3. Final Answer:

   It breaks the text into parts based on a separator. -> Option A

4. Quick Check:

   Split means break text apart [OK]

Hint: Split means break text into pieces by separator [OK]

Common Mistakes:

• Confusing split with join or merge
• Thinking split removes spaces instead of using them as separators
• Assuming split converts data types

2. Which of the following is the correct syntax to split a pandas column 'Name' by spaces into multiple columns?

easy

A. df['Name'].split(expand=True)

B. df['Name'].split(' ')

C. df.str.split(' ', 'Name')

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

Solution

1. Step 1: Recall pandas string method syntax

   Use str.split() on a Series with expand=True to get multiple columns.

2. Step 2: Check each option

   df['Name'].split(' ') misses str, C has wrong argument order, D misses separator argument.

3. Final Answer:

   df['Name'].str.split(' ', expand=True) -> Option D

4. Quick Check:

   Use str.split with expand=True [OK]

Hint: Use df['col'].str.split(sep, expand=True) for columns [OK]

Common Mistakes:

• Forgetting to use .str before split
• Not setting expand=True to get multiple columns
• Passing wrong arguments or order

3. Given the DataFrame:

import pandas as pd
df = pd.DataFrame({'FullName': ['Alice Smith', 'Bob Jones', 'Carol Lee']})
df[['First', 'Last']] = df['FullName'].str.split(' ', expand=True)
print(df)

What will be the output?

medium

A. A DataFrame with columns FullName, First, Last where First and Last contain split names.

B. An error because split cannot create multiple columns.

C. A DataFrame with only First and Last columns, FullName removed.

D. A DataFrame with FullName column unchanged and First column with full names.

Solution

1. Step 1: Understand the split with expand=True

   Splitting 'FullName' by space creates two columns: 'First' and 'Last'.

2. Step 2: Check DataFrame structure after assignment

   Original 'FullName' stays, new columns 'First' and 'Last' are added with split parts.

3. Final Answer:

   A DataFrame with columns FullName, First, Last where First and Last contain split names. -> Option A

4. Quick Check:

   Split with expand=True adds columns [OK]

Hint: expand=True adds new columns, original stays [OK]

Common Mistakes:

• Expecting original column to be removed
• Thinking split returns a list inside one column
• Confusing expand=True effect

4. What is wrong with this code snippet?

df['City', 'State'] = df['Location'].str.split(',', expand=True)

medium

A. expand=True should be False to assign multiple columns.

B. The split separator ',' is incorrect for splitting locations.

C. You cannot assign multiple columns using a tuple as column names like ('City', 'State').

D. The code is correct and will work without errors.

Solution

1. Step 1: Check assignment syntax for multiple columns

   Assigning multiple columns requires a list of column names, not a tuple.

2. Step 2: Identify correct syntax

   Use df[['City', 'State']] = ... with double brackets for multiple columns.

3. Final Answer:

   You cannot assign multiple columns using a tuple as column names like ('City', 'State'). -> Option C

4. Quick Check:

   Use double brackets for multiple columns [OK]

Hint: Use double brackets [[]] to assign multiple columns [OK]

Common Mistakes:

• Using single brackets with tuple for multiple columns
• Confusing expand=True with assignment syntax
• Assuming tuple works like list for columns

5. You have a DataFrame with a column 'Tags' containing strings like 'red,blue,green'. You want to create a new DataFrame where each tag is a separate row linked to the original row index. Which pandas method combined with str.split() helps achieve this?

hard

A. Use str.split(',', expand=True) to create multiple columns.

B. Use str.split(',').explode() to split and expand tags into rows.

C. Use str.split(',').apply(list) to convert tags to lists.

D. Use str.split(',').join() to merge tags back.

Solution

1. Step 1: Understand the goal to expand tags into rows

   Splitting creates lists; explode() turns list elements into separate rows.

2. Step 2: Evaluate options for correct method

   Use str.split(',').explode() to split and expand tags into rows. correctly chains str.split() with explode() to get one tag per row.

3. Final Answer:

   Use str.split(',').explode() to split and expand tags into rows. -> Option B

4. Quick Check:

   Split then explode = rows per item [OK]

Hint: Split then explode to get rows per list item [OK]

Common Mistakes:

• Using expand=True creates columns, not rows
• Forgetting to use explode() after split
• Confusing join() with explode()