Load Specific Worksheets in a Workbook with Python.NET

By default, Aspose.Cells loads the whole spreadsheet into memory. Developers can load only specific sheets to improve performance and reduce memory consumption. This approach is particularly useful when working with large workbooks containing many worksheets.

import os
from aspose.cells import Workbook, LoadOptions, LoadFormat, LoadFilter

class CustomLoad(LoadFilter):
    def __init__(self):
        super().__init__()
        self.sheets_in_loading_order = [0]  # Load first worksheet only

# The path to the documents directory.
current_dir = os.path.dirname(os.path.abspath(__file__))
data_dir = os.path.join(current_dir, "data")

# Load the workbook with the specified worksheet only.
load_options = LoadOptions(LoadFormat.XLSX)
load_options.load_filter = CustomLoad()

# Create the workbook
workbook = Workbook(os.path.join(data_dir, "TestData.xlsx"), load_options)

# Perform your desired task

# Save the workbook
output_dir = os.path.join(current_dir, "output")
if not os.path.exists(output_dir):
    os.makedirs(output_dir)

workbook.save(os.path.join(output_dir, "outputFile.out.xlsx"))

The following Python.NET code demonstrates how to implement the CustomLoad class:

import aspose.cells as ac

class CustomLoad(ac.LoadFilter):
    def start_sheet(self, sheet):
        # Only load sheets named "Sheet1" or "Sheet2"
        if sheet.name in ["Sheet1", "Sheet2"]:
            return True
        return False

# Create load options with custom filter
load_options = ac.LoadOptions()
load_options.load_filter = CustomLoad()
load_options.load_data_filter_options = ac.LoadDataFilter.STRUCTURE

# Load workbook with filtered worksheets
workbook = ac.Workbook("large_workbook.xlsx", load_options)

# Access loaded worksheet
print(f"First loaded sheet: {workbook.worksheets[0].name}")

from aspose.cells import LoadFilter, LoadDataFilterOptions, Worksheet

class CustomLoad(LoadFilter):
    def start_sheet(self, sheet: Worksheet):
        if sheet.name == "Sheet2":
            # Load everything from worksheet "Sheet2"
            self.load_data_filter_options = LoadDataFilterOptions.ALL
        else:
            # Load nothing
            self.load_data_filter_options = LoadDataFilterOptions.STRUCTURE

Key implementation details:

1. Inherit from LoadFilter abstract base class
2. Override start_sheet method with Python’s snake_case naming
3. Use LoadDataFilter.STRUCTURE enum for data filtering
4. Implement conditional loading based on worksheet names
5. Use Python-style path handling and string comparisons

This approach significantly reduces memory usage when working with large Excel files by only loading specified worksheets while maintaining access to the workbook’s structure.