9.1 Naming Conventions

Variable names (also called identifiers) in Python have to follow the following rules:

• may contain letters or digits, but cannot start with a digit;
• may contain underscore (_) characters and may start with an underscore; and
• may not contain spaces or other special characters.
• Never use l (lowercase L), O (uppercase o), or I(uppercase i) single letter names as these can be mistaken for 1 (one) and 0 (zero), depending on typeface

Thus, KyloRen, IG88, and luke_Skywalker are valid variable names, but these are not: Luke+Leia_4_Evar (contains special character +), 2ManyStormTroopers (starts with a digit), and Han Shot First (contains spaces).