Library

Everything you need to level up your coding skills.

XML

Python ParseError Unbound Prefix in XML and How to Fix It

Fix ElementTree ParseError unbound prefix and lxml Namespace prefix is not defined: fragments cut from a document, auto-declared prefixes, recover.

7 min read

YAML

YAML Error Found Character That Cannot Start Any Token

Which characters trigger this scanner error, a tab, at sign, backtick or percent sign, what each looks like in output and the fix that clears it.

6 min read

XML

Mismatched Tag Errors in Large XML Files and Finding Them

Locate an Opening and ending tag mismatch in a 28.6 MB XML file four ways: the parser, per-tag counts, record-by-record parsing and bisection, with timings.

6 min read

JSON

Fixing JSON Copied From a Web Page With Smart Quotes

JSON pasted from a web page, a chat or a Word file fails on curly quotes and invisible spaces. How to spot each character and clean the text safely.

8 min read

YAML

YAML Error Mapping Values Are Not Allowed Here Fixed

What mapping values are not allowed here means, three causes found in real files, an unquoted colon, a stray space and a double value, and the fix for each.

6 min read

XML

Content Is Not Allowed in Prolog and the Hidden BOM

What Content is not allowed in prolog means in Java: a BOM decoded to text, a double BOM, JSON or text instead of XML, and how to diagnose it.

6 min read

JSON

Finding the Exact Line of a JSON Syntax Error in Any Parser

Every JSON parser reports a position in a different way. How to turn a character offset into a line, a column and a caret in Python, Node and jq.

9 min read

XML

Undefined Entity Errors in XML and the Ampersand Problem

Fix undefined entity and Entity not defined errors in XML from HTML entities like nbsp and eacute: convert to numeric references, a DOCTYPE, or lxml recover.

6 min read

YAMLGuide

Fixing YAML Errors That Make No Sense Step by Step

A YAML debugging guide: the error catalog across three parsers, a worked session through five stacked mistakes, silent failures and tools to prevent them.

20 min read

JSON

JSON Parse Error Single Quotes Instead of Double Quotes

JSON needs double quotes, but a Python repr or JavaScript literal uses single quotes. What each parser says, why replacing quotes breaks, and safe fixes.

6 min read

XML

Invalid Character in XML and Stripping Control Characters

Fix PCDATA invalid Char value and reference to invalid character number: which characters XML 1.0 forbids, how to strip them from 28 MB in 0.03 s and verify.

6 min read

JSON

Unexpected End of JSON Input and How to Find the Cause

Unexpected end of JSON input means the text stopped too soon or was empty. Real messages for every cut point, and how to tell truncated from empty.

8 min read

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