Joining Strings and Extracting Data with Regex in Pandas

As a data analyst or scientist, working with string data is an essential part of your job. Regular expressions (regex) can be used to extract specific patterns from these strings, making it easier to clean, transform, and analyze the data.

In this article, we’ll explore how to join two strings within a list regex in Pandas, a popular Python library for data manipulation and analysis. We’ll also cover extracting specific parts of a string using regex.

Understanding the Problem

The problem presented involves joining two strings within a list extracted from a column using regex. The desired output is to combine these two strings with an underscore (_) separator. Additionally, we need to extract another part of the original string using regex.

Data Preparation

To demonstrate this process, let’s first create a sample DataFrame df with columns ‘A’ and ‘B’. Column ‘A’ contains strings from which we want to extract two parts: one that will be used as a separator for joining the two lists, and another part that we’ll use for extraction using regex.

import pandas as pd

# Create sample data
data = {
    'A': ['R13_IR_T20I1E7_PP3_S1_N002_V087_1785984_12593', 
          'R13_IR_T20I1E7_PP3_S1_N003_V023_5896589_15105', 
          'R13_IR_T20I1E7_PP3_S1_N004_V155_2541236_11033'],
    'B': ['["S1", "V087"]', '["S1", "V023"]', '["S1", "V155"]]
}

# Convert the list values in column B to string
df['B'] = df['B'].apply(lambda x: '['.join(x) if isinstance(x, list) else x)

print(df)

Output:

Joining Strings in List Regex

To join the two strings within the list regex, we can use the str.join() function.

# Join the strings in column B with an underscore
df['B'] = df['B'].apply(lambda x: '['.join(x).strip('[]').replace("'", "") + '_' + '['.join(x).strip('[]').replace("'", '') if isinstance(x, list) else x)

print(df)

Output:

Extracting Data with Regex

To extract another part of the original string, we’ll use regex. We’re interested in extracting the number part followed by an underscore and then a number.

# Import necessary libraries
import pandas as pd

# Create sample data
data = {
    'A': ['R13_IR_T20I1E7_PP3_S1_N002_V087_1785984_12593', 
          'R13_IR_T20I1E7_PP3_S1_N003_V023_5896589_15105', 
          'R13_IR_T20I1E7_PP3_S1_N004_V155_2541236_11033'],
    'C': ['S1_' + df['A'].str.extract("(\\d+)_\\d+$").astype(str) if isinstance(df['A'].iloc[0], list) else '' for _ in range(3)]
}

# Convert the list values in column C to string
df = pd.DataFrame(data)

print(df)

Output:

In this article, we covered how to join two strings within a list regex in Pandas using str.join(). We also explored extracting another part of the original string using regex.

Last modified on 2024-01-07