}

Solved errors

Direct solutions to common programming errors and system issues.

Page 2 of 17

golang go undefined error compile
6 min readBeginner

Fix Golang 'undefined: function' Error — All Causes (2026)

Fix the Golang 'undefined: functionName' compile error. Covers missing imports, wrong package, typos, unexported names, and wrong module path with before/after code.

python error AttributeError NoneType debugging
5 min readBeginner

Fix Python AttributeError: 'X' object has no attribute 'Y' (2026)

Fix Python AttributeError 'X' object has no attribute 'Y'. Covers None from functions, typos, missing self.attr in __init__, wrong types, module errors, hasattr and getattr.

python error IndentationError TabError tabs
4 min readBeginner

Fix Python IndentationError and TabError: Tabs vs Spaces (2026)

Fix Python IndentationError unexpected indent and TabError inconsistent use of tabs and spaces. Covers PEP 8, VS Code, vim retab, python -tt, and .editorconfig.

python error ModuleNotFoundError pip import
4 min readBeginner

Fix Python ModuleNotFoundError: No module named 'X' (2026)

Fix Python ModuleNotFoundError: No module named 'X'. Covers pip install, wrong Python version, venv not activated, sys.path debugging, and import name differences.

python error TypeError subscriptable NoneType
4 min readBeginner

Fix Python 'TypeError: X object is not subscriptable' (2026)

Fix Python TypeError 'NoneType' object is not subscriptable. Covers what subscriptable means, NoneType from None-returning functions, int/float errors, and isinstance checks.

linux networking rfkill wifi error
5 min readBeginner

Fix "RTNETLINK answers: Operation not possible due to RF-kill" in Linux

Fix "RTNETLINK answers: Operation not possible due to RF-kill" on Linux. Covers rfkill list, rfkill unblock, hardware switch, and NetworkManager solutions.

SAP error ABAP configuration MM
8 min readIntermediate

SAP Error Message 00058: Entry Does Not Exist — All Scenarios and Fixes

Fix SAP Message 00058 'Entry does not exist in table'. Covers all scenarios: T005E, SKB1, T685, T007A, SECCODE, ABAP ALV. Step-by-step solutions for each table.

ssh linux networking sysadmin firewall
5 min readBeginner

Fix SSH 'Connection Refused' Error — All Causes (2026)

Fix "ssh: connect to host port 22: Connection refused". All causes: SSH not running, wrong port, firewall, fail2ban ban. Diagnostic flow with nc and nmap.

ssh linux security sysadmin networking
6 min readBeginner

Fix SSH 'Host Key Verification Failed' Error (2026)

Fix "WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! Host key verification failed." Safe steps: ssh-keygen -R, known_hosts edit, StrictHostKeyChecking options explained.

Go Golang Programming macOS Linux
11 min readIntermediate

compile: version does not match go tool version — Fix in 60 Seconds

Fix "compile: version does not match go tool version" in Go. Caused by GOROOT mismatch, stale PATH, or multiple Go installs. Copy-paste fix for Linux, macOS, and Windows.