Building a Simple Spreadsheet Engine in Python

 Spreadsheets are powerful tools for organizing and calculating data. In this post, we’ll walk through how to build a basic spreadsheet engine in Python that supports cell updates, resets, and formula evaluation.

🧩 Problem Overview

We need to implement a spreadsheet with:

• 26 columns labeled 'A' to 'Z'

• A user-defined number of rows

• Each cell can store an integer between 0 and 10^5

• Support for formulas like =A1+B2+5, where operands can be cell references or integers

🛠️ Class Design

We’ll use a dictionary to store only the cells that have been explicitly set. Unset cells are treated as having a value of 0.

python

class Spreadsheet:

    def __init__(self, rows: int):
        self.mpp = {}

    def setCell(self, cell: str, value: int) -> None:
        self.mpp[cell] = value     

    def resetCell(self, cell: str) -> None:
        self.mpp[cell] = 0

    def getValue(self, formula: str) -> int:
        new_text = formula.replace("=", "+")
        parts = new_text.split('+')
        total = 0
        for part in parts:
            part = part.strip()
            if part in self.mpp:
                total += self.mpp[part]
            elif part.isdigit():
                total += int(part)
        return total

🧪 Example Usage

python

# Initialize spreadsheet with 10 rows
obj = Spreadsheet(10)

# Set cell A1 to 10
obj.setCell("A1", 10)

# Reset cell B! (treated as valid input, reset to 0)
obj.resetCell("B!")

# Evaluate formula "A1" (no '=' or '+', treated as single cell reference)
param_3 = obj.getValue('A1')
print(param_3)  # Output: 10

🔍 Notes

• The getValue method replaces = with + to normalize the formula, then splits it by +.

• Each part is checked: if it’s a digit, it’s added directly; if it’s a cell reference, its value is fetched from the dictionary.

• Unset cells default to 0 using dict.get() logic.

📦 Enhancements

This basic engine can be extended to support:

• Cell ranges like A1:A3

• More operators (-, *, /)

• Dependency tracking and auto-updates

This implementation is efficient and handles up to 10⁴ operations smoothly. Perfect for interview prep or building lightweight spreadsheet logic into a Python app.

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