How-To Guides

Fixing Python openpyxl That Fails to Apply Number Formatting to Cells

You've set a number format in openpyxl, saved the file, opened it in Excel — and the cells still look plain. Here's exactly why that happens and how to fix it for currencies, dates, percentages, and more.

Jun 17, 2026 9m read 👁 3

Fixing Python openpyxl That Writes Data to the Wrong Sheet Tab

Your openpyxl script runs without errors, but the data lands on the wrong sheet tab — or worse, a brand-new sheet you never asked for. Here's exactly why it happens and how to fix it for good.

Jun 17, 2026 8m read 👁 1

Fixing Python openpyxl That Reads Excel Formulas Instead of Values

openpyxl is returning the formula string like '=SUM(A1:A10)' instead of the calculated result? You're not alone. This guide explains exactly why it happens and shows every reliable fix.

Jun 17, 2026 8m read 👁 2

Fixing Excel XLOOKUP That Returns #N/A When the Match Exists

Your XLOOKUP formula looks right, the value is clearly there, but Excel keeps throwing #N/A. Here's a systematic breakdown of every common cause and how to fix each one fast.

Jun 17, 2026 8m read 👁 3

Fixing Excel COUNTIFS That Returns Zero With Date Range Criteria

COUNTIFS returning zero on a date range is one of Excel's most frustrating silent failures. The formula looks right, the dates are there, but the count is always 0. Here's exactly why it happens and how to fix it fast.

Jun 17, 2026 8m read 👁 5

Fixing Python requests That Hang Indefinitely Without Raising a Timeout Error

Your Python script fires off an HTTP request and then just... sits there. No error, no response, no way to know when it will finish. Here's exactly why requests hangs silently and how to fix it for good.

Jun 16, 2026 9m read 👁 3

Fixing Python datetime.strptime That Raises ValueError on Valid Date Strings

Your date string looks perfectly valid, yet datetime.strptime keeps throwing a ValueError. This guide walks through every common mismatch — format codes, locales, whitespace, and more — so you can fix it fast.

Jun 16, 2026 8m read 👁 3

Fixing Excel INDEX MATCH That Returns the Wrong Row When Data Is Unsorted

INDEX MATCH is supposed to be more flexible than VLOOKUP, but it still silently returns wrong results when your data isn't sorted the way the formula expects. Here's exactly why it happens and how to fix it fast.

Jun 16, 2026 6m read 👁 3

Fixing Python sqlite3 Queries That Return No Rows Despite Matching Data

Your SQLite query runs without errors, but fetchall() hands back an empty list — even though the data is clearly there. Here are the most common causes and how to squash each one fast.

Jun 16, 2026 9m read 👁 3

Fixing PostgreSQL Queries That Slow Down After Table Rows Exceed 1 Million

Your PostgreSQL queries were fast at 100k rows, but now that the table has crossed a million records, everything crawls. Here's exactly what's happening and how to fix it without rewriting your entire schema.

Jun 16, 2026 9m read 👁 2

Fixing Pandas read_csv That Silently Misreads Date Columns as Strings

Pandas read_csv loads your date columns as plain strings without any warning, and every downstream calculation breaks quietly. Here's exactly how to detect the problem and fix it for good.

Jun 15, 2026 8m read 👁 2

Fixing Excel SUMIF That Returns Zero When Criteria Look Correct

Your SUMIF formula looks perfect but keeps returning zero. The data is right there. This guide walks through every real cause — from invisible spaces to number-stored-as-text — and shows you exactly how to fix each one.

Jun 15, 2026 8m read 👁 3