Read multiple CSV files from a directory and write them into a single Excel (.xlsx) file. Each CSV file becomes one sheet in the workbook.

Available in Java and Python.

Python

Requirements

  • Python 3.10+
  • pip

Setup

pip install -r requirements.txt

Run

# Use current directory as input, output to output.xlsx
python csv_to_excel.py
# or: python3 csv_to_excel.py

# Specify input directory and output file
python csv_to_excel.py /path/to/csv/folder result.xlsx

# Only input directory (output defaults to output.xlsx)
python csv_to_excel.py sample-data

Example with sample data:

python csv_to_excel.py sample-data my-report.xlsx

Java

Requirements

  • Java 17 or later
  • Maven 3.6+

Build

mvn clean package

This produces:

  • target/csv-to-excel-1.0.0.jar — normal JAR (requires classpath)
  • target/csv-to-excel-jar-with-dependencies.jar — runnable JAR with all dependencies (use this to run)

Run

Using the runnable JAR (recommended):

# Use current directory as input, output to output.xlsx
java -jar target/csv-to-excel-jar-with-dependencies.jar

# Specify input directory and output file
java -jar target/csv-to-excel-jar-with-dependencies.jar /path/to/csv/folder result.xlsx

# Only input directory (output defaults to output.xlsx)
java -jar target/csv-to-excel-jar-with-dependencies.jar /path/to/csv/folder

Using Maven:

mvn exec:java -Dexec.mainClass="com.csvtoexcel.CsvToExcel" -Dexec.args="/path/to/csv/folder result.xlsx"

(For exec:java you need the exec-maven-plugin; the JAR approach above is simpler.)

Behavior

  • Input: A directory containing one or more .csv files (by name, case-insensitive).
  • Output: One .xlsx file. Sheet names are derived from CSV file names (extension removed, invalid characters replaced, length limited to 31 characters).
  • Encoding: CSV files are read as UTF-8.
  • Header: The first row of each CSV is treated as the header and is written as the first row of the corresponding sheet.

Example

If ./data/ contains sales.csv, inventory.csv, and users.csv, then:

java -jar target/csv-to-excel-jar-with-dependencies.jar ./data report.xlsx

creates report.xlsx with three sheets: sales, inventory, and users.

A sample-data/ folder with example CSVs is included for quick testing (use either Java or Python as above).