How to debug in PyCharm (PyCharm debugger tutorial) [+ Common Mistakes !]

Tutorial Overview

This tutorial demonstrates how to use PyCharm’s debugger to follow Python code execution, inspect values, and investigate functions.

Breakpoints

Click the editor gutter beside a line to set or remove a breakpoint. When debugging, execution pauses before the marked line runs. The presenter starts a debugging session by right-clicking in the editor and selecting Debug.

Stepping Through Code

• Step Over (F8) runs the highlighted line and advances to the next one without entering functions called by that line. The presenter uses it to trace a loop that builds a list of doubled values.
• Step Into My Code enters functions and classes written by the developer.
• Step Into can also enter library or package code, such as Python’s random module.
• Step Out returns from the current function or library code.

Inspecting Values

The debugger’s Variables panel shows current variable values as the program runs. Evaluate Expression lets you test expressions in the current debugging context, such as converting range(1, 6) to a list or calculating i * 2.

You can also add expressions as watches to track their values across steps—for example, i * 3. The tutorial demonstrates adding watches with Ctrl+Shift+Enter, removing and reordering them, showing or hiding the evaluate field, and separating watches from the Variables panel.

Continuing Between Breakpoints

The presenter demonstrates continuing execution until the next breakpoint. Although the subtitles call this control “step out,” the described behavior is normally Resume Program, not Step Out.

Breakpoint on the First Line

The presenter reports that, in their test, a breakpoint on the first line caused PyCharm’s debugging to behave incorrectly. They found that adding a blank line before the code worked around the issue and reported no such problem in DataSpell or VS Code. This is the presenter’s observation, not a general guarantee.

Main speaker/source: A single presenter from the Koolac channel.