Understanding Openpyxl and the wb.save() TypeError

Openpyxl is a popular Python library for working with Excel files. It allows developers to read, write, and modify Excel workbooks (.xlsx, .xlsm, .xltx, .xltm) in a programmatic way. In this article, we’ll delve into the world of Openpyxl and explore the wb.save() function that’s causing a TypeError.

The Error

When running the code snippet provided by the questioner, we encounter two errors:

  File "C:\Users\AppData\Local\Programs\Python\Python310\lib\site-packages\openpyxl\descriptors\base.py", line 55, in _convert
    value = expected_type(value)
TypeError: Fill() takes no arguments


During handling of the above exception, another exception occurred:

  File "C:\Users\AppData\Local\Programs\Python\Python310\lib\site-packages\openpyxl\descriptors\base.py", line 57, in _convert
    raise TypeError('expected ' + str(expected_type))
TypeError: expected <class 'openpyxl.styles.fills.Fill'>&gt;

These errors occur when attempting to save an Excel workbook using the wb.save() function.

Understanding Openpyxl’s Workbook Structure

Before we dive into the solution, let’s review how Openpyxl represents a workbook. An Openpyxl workbook consists of multiple sheets (or tabs), which are stored in a dictionary called sheets. Each sheet is an instance of the Worksheet class, which contains various elements such as:

Cells
Rows
Columns

Openpyxl also introduces the concept of styles, which define formatting options for cells and other elements. Styles can be applied to specific ranges or individual cells.

The Problem with wb.save()

In this article, we’ll explore why the wb.save() function is throwing a TypeError when attempting to save an Excel workbook. We’ll examine how Openpyxl handles styles and cell formatting to shed some light on the issue.

Styles in Openpyxl

When working with Openpyxl, it’s essential to understand that style objects are not directly accessible through the wb.save() function. Instead, styles are defined as part of a workbook’s structure, using various methods such as:

workbook.create_style()
style = workbook.add_format()

Here is an example:

from openpyxl import Workbook

# Create a new workbook
wb = Workbook()

# Select the first sheet
sheet = wb.active

# Define some styles
style = wb.add_format({'bg_color': 'A7E9B8'})

# Apply the style to cells
for row in range(1, 5):
    for col in range(1, 3):
        cell = sheet.cell(row=row, column=col)
        cell.font = {'bold': True}
        if row == 2:
            cell.fill = style

Filling Cells with Styles

Now that we’ve covered styles and how they’re defined, let’s explore filling cells with these styles. Filling cells involves applying a specific style to a range of cells.

Here is an example:

# Fill cells with the defined style
sheet['A1:E3'].fill = {'bg_color': 'F2C464'}

The Solution

Based on our understanding of Openpyxl’s workbook structure and how styles are handled, we can identify the issue that’s causing the wb.save() TypeError. The problem lies in attempting to pass a style object directly as an argument when calling the wb.save() function.

To fix this issue, you need to either:

Remove all references to fill() or background_color from any code snippets.
Pass a dictionary containing your desired fill color with style name

Fill cells with the defined style

sheet[‘A1:E3’].fill = {‘fill’: {‘bg_color’: ‘F2C464’}}


In our previous code snippet we had already included this correction:

```markdown
from openpyxl import Workbook

# Create a new workbook
wb = Workbook()

# Select the first sheet
sheet = wb.active

# Define some styles
style = wb.add_format({'bg_color': 'A7E9B8'})

# Fill cells with the defined style
for row in range(1, 5):
    for col in range(1, 3):
        cell = sheet.cell(row=row, column=col)
        cell.font = {'bold': True}
        if row == 2:
            cell.fill = style

By making these changes, we can avoid the TypeError that’s occurring when attempting to save an Excel workbook using the wb.save() function.

Conclusion

Openpyxl provides a powerful and flexible way to work with Excel files in Python. However, it’s essential to understand how styles and cell formatting are handled within the library.

By making small adjustments to your code snippets, such as ensuring fill() or background_color is passed correctly when calling wb.save() , you can resolve errors like the TypeError that was encountered in this example.

We hope that by understanding the underlying principles of Openpyxl’s structure, styles, and functions you will be able to overcome similar issues with confidence.

Last modified on 2025-01-09