Concepts·Certified Entry-Level Python Programmer

Python Scope, Shadowing and global

The environment half of objective 4.2. Python resolves a name through four scopes - local, enclosing, global, built-in - and decides whether a name is local by looking for an assignment *anywhere* in the function, including below the line that reads it. That single rule produces `UnboundLocalError`, which is the most confusing error in the objective and completely predictable once you know what causes it.

Functions and Scope Guide 20 of 26 Intermediate

Python3.14.4
OSUbuntu 26.04 LTS
pip25.1.1
TimeAbout 17 min
Reviewed23 August 2026

Written against the versions above. `nonlocal` arrived in Python 3.0 and is the one keyword here that Python 2 does not have. The `UnboundLocalError` message was reworded in Python 3.11 to name the variable; the behaviour is unchanged.

One machine, and any shell with Python 3 will do - these exams test the language, not a distribution.
Server Name	IP Address	OS	Roles	CPU	RAM	HDD
RUNNER01	192.168.0.27	Ubuntu 26.04 LTS	Python 3.14.4 - the only machine this path needs	2 Core	4 GB	50 GB

Before you start

guide 19 - parameters are locals.
guide 18 - a def creates a name like any other.

Reading a global, and shadowing one
The read that fails because of a line below it
global: assign to the module-level name
nonlocal: assign to the enclosing function's name
The four scopes, innermost first
A local exists only while the call does
What the exam does with this objective

Official sources

← All PCEP guides

Python Scope, Shadowing and global

Before you start

Reading a global, and shadowing one

The read that fails because of a line below it

global: assign to the module-level name

nonlocal: assign to the enclosing function's name

The four scopes, innermost first

A local exists only while the call does

What the exam does with this objective

Official sources