Glossary

Type inference

A tool guessing column types from the values it reads, for example turning 02139 into the number 2139.

CSV has no types, so readers guess. pandas.read_csv infers numbers and dates by default and can drop leading zeros or misread day/month. Read raw files as text and convert each column with an explicit, validated rule.

Lesson: Import everything as text first
Practise: Keep identifiers as text and parse yes/no flags

Related: Leading zeros, Identifier, Schema