Python csv for excel

There are many common file types that you will need to work with as a software developer. One such format is the CSV file. CSV stands for “Comma-Separated Values” and is a text file format that uses a comma as a delimiter to separate values from one another. Each row is its own record and each value is its own field. Most CSV files have records that are all the same length.

Microsoft Excel opens CSV files with no problem. You can open one yourself with Excel and then save it yourself in an Excel format. The purpose of this article is to teach you the following concepts:

• Converting a CSV file to Excel
• Converting an Excel spreadsheet to CSV

You will be using Python and OpenPyXL to do the conversion from one file type to the other.

Getting Started

You need to install OpenPyXL to be able to use the examples in this article. You can use pip to install OpenPyXL:

python3 -m pip install openpyxl

Now that you have OpenPyXL, you are ready to learn how to convert a CSV file to an Excel spreadsheet!

You will soon see that converting a CSV file to an Excel spreadsheet doesn’t take very much code. However, you do need to have a CSV file to get started. With that in mind, open up your favorite text editor (Notepad, SublimeText, or something else) and add the following:

book_title,author,publisher,pub_date,isbn
Python 101,Mike Driscoll, Mike Driscoll,2020,123456789
wxPython Recipes,Mike Driscoll,Apress,2018,978-1-4842-3237-8
Python Interviews,Mike Driscoll,Packt Publishing,2018,9781788399081

Save this file as books.txt. You can also download the CSV file from this book’s GitHub code repository.

Now that you have the CSV file, you need to create a new Python file too. Open up your Python IDE and create a new file named csv_to_excel.py. Then enter the following code:

# csv_to_excel.py

import csv
import openpyxl


def csv_to_excel(csv_file, excel_file):
    csv_data = []
    with open(csv_file) as file_obj:
        reader = csv.reader(file_obj)
        for row in reader:
            csv_data.append(row)

    workbook = openpyxl.Workbook()
    sheet = workbook.active
    for row in csv_data:
        sheet.append(row)
    workbook.save(excel_file)


if __name__ == "__main__":
    csv_to_excel("books.csv", "books.xlsx")

Your code uses Python’s csv module in addition to OpenPyXL. You create a function, csv_to_excel(), then accepts two arguments:

• csv_file – The path to the input CSV file
• excel_file – The path to the Excel file that you want to create

You want to extract each row of data from the CSV. To extract the data, you create an csv.reader() object and then iterate over one row at a time. For each iteration, you append the row to csv_data. A row is a list of strings.

The next step of the process is to create the Excel spreadsheet. To add data to your Workbook, you iterate over each row in csv_data and append() them to your Worksheet. Finally, you save the Excel spreadsheet.

When you run this code, you will have an Excel spreadsheet that looks like this:

You are now able to convert a CSV file to an Excel spreadsheet in less than twenty-five lines of code!

Now you are ready to learn how to convert an Excel spreadsheet to a CSV file!

Converting an Excel Spreadsheet to CSV

Converting an Excel spreadsheet to a CSV file can be useful if you need other processes to consume the data. Another potential need for a CSV file is when you need to share your Excel spreadsheet with someone who doesn’t have a spreadsheet program to open it. While rare, this may happen.

You can convert an Excel spreadsheet to a CSV file using Python. Create a new file named excel_to_csv.py and add the following code:

# excel_to_csv.py

import csv
import openpyxl

from openpyxl import load_workbook


def excel_to_csv(excel_file, csv_file):
    workbook = load_workbook(filename=excel_file)
    sheet = workbook.active
    csv_data = []
    
    # Read data from Excel
    for value in sheet.iter_rows(values_only=True):
        csv_data.append(list(value))

    # Write to CSV
    with open(csv_file, 'w') as csv_file_obj:
        writer = csv.writer(csv_file_obj, delimiter=',')
        for line in csv_data:
            writer.writerow(line)


if __name__ == "__main__":
    excel_to_csv("books.xlsx", "new_books.csv")

Once again you only need the csv and openpyxl modules to do the conversion. This time, you load the Excel spreadsheet first and iterate over the Worksheet using the iter_rows method. The value you receive in each iteration of iter_tools is a list of strings. You append the list of strings to csv_data.

The next step is to create a csv.writer(). Then you iterate over each list of strings in csv_data and call writerow() to add it to your CSV file.

Once your code finishes, you will have a brand new CSV file!

Wrapping Up

Converting a CSV file to an Excel spreadsheet is easy to do with Python. It’s a useful tool that you can use to take in data from your clients or other data sources and transform it into something that you can present to your company.

You can apply cell styling to the data as you write it to your Worksheet too. By applying cell styling, you can make your data stand out with different fonts or background row colors.

Try this code out on your own Excel or CSV files and see what you can do.

Related Reading

Would you like to learn more about processing Excel spreadsheets with Python? Then check out these tutorials:

• OpenPyXL – Working with Microsoft Excel Using Python

• Styling Excel Cells with OpenPyXL and Python

• Reading Excel Spreadsheets with Python and xlrd

Problem Formulation

💡 Challenge: Given a CSV file. How to convert it to an excel file in Python?

We create a folder with two files, the file csv_to_excel.py and my_file.csv. We want to convert the CSV file to an excel file so that after running the script csv_to_excel.py, we obtain the third file my_file.csv in our folder like so:

All methods discussed in this tutorial show different code snippets to put into csv_to_excel.py so that it converts the CSV to XLSX in Python.

Method 1: 5 Easy Steps in Pandas

The most pythonic way to convert a .csv to an .xlsx (Excel) in Python is to use the Pandas library.

1. Install the pandas library with pip install pandas
2. Install the openpyxl library that is used internally by pandas with pip install openpyxl
3. Import the pandas libray with import pandas as pd
4. Read the CSV file into a DataFrame df by using the expression df = pd.read_csv('my_file.csv')
5. Store the DataFrame in an Excel file by calling df.to_excel('my_file.xlsx', index=None, header=True)

import pandas as pd


df = pd.read_csv('my_file.csv')
df.to_excel('my_file.xlsx', index=None, header=True)

Note that there are many ways to customize the to_excel() function in case

• you don’t need a header line,
• you want to fix the first line in the Excel file,
• you want to format the cells as numbers instead of strings, or
• you have an index column in the original CSV and want to consider it in the Excel file too.

If you want to do any of those, feel free to read our full guide on the Finxter blog here:

🌍 Tutorial: Pandas DataFrame.to_excel() – An Unofficial Guide to Saving Data to Excel

Also, we’ve recorded a video on the ins and outs of this method here:

Let’s have a look at an alternative to converting a CSV to an Excel file in Python:

Method 2: Modules csv and openpyxl

To convert a CSV to an Excel file, you can also use the following approach:

• Import the csv module
• Import the openpyxl module
• Read the CSV file into a list of lists, one inner list per row, by using the csv.reader() function
• Write the list of lists to the Excel file by using the workbook representation of the openpyxl library.
• Get the active worksheet by calling workbook.active
• Write to the worksheet by calling worksheet.append(row) and append one list of values, one value per cell.

The following function converts a given CSV to an Excel file:

import csv
import openpyxl


def csv_to_excel(csv_filename, excel_filename):

    # Read CSV file
    csv_data = []
    with open(csv_filename) as f:
        csv_data = [row for row in csv.reader(f)]
    
    # Write to Excel file
    workbook = openpyxl.workbook.Workbook()
    worksheet = workbook.active
    for row in csv_data:
        worksheet.append(row)
    workbook.save(excel_filename)


if __name__ == "__main__":
    csv_to_excel("my_file.csv", "my_file.xlsx")

This is a bit more fine-granular approach and it allows you to modify each row in the code or even write additional details into the Excel worksheet.

More Python CSV Conversions

🐍 Learn More: I have compiled an “ultimate guide” on the Finxter blog that shows you the best method, respectively, to convert a CSV file to JSON, Excel, dictionary, Parquet, list, list of lists, list of tuples, text file, DataFrame, XML, NumPy array, and list of dictionaries.

Where to Go From Here?

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