Variables and Values

Python's variables aren't buckets that contain things. They're pointers that reference objects.

The way Python's variables work can often confuse folks new to Python, both new programmers and folks moving from other languages like C++ or Java.

Below are 9 minutes of screencasts explaining how Python's variables and values work. If you prefer reading over watching, you can find the transcript for each screencast below each video.

Screencasts (including transcripts)

1. Variables are Pointers
2. The 2 Types of "Change" in Python
3. Equality vs Identity
4. Data Structures Contain Pointers

Other Resources

Talks I recommend on this subject:

• Facts and Myths about Python names and values by Ned Batchelder: false assumptions programmers make about variables in Python
• Names Objects and Plummeting From The Cliff by Brandon Rhodes: a visual demonstration of Python's variable handling and garbage collection

Articles I recommend on this subject:

• Is Python call-by-value or call-by-reference? Neither. by Jeff Knupp: this will make more sense after watching the talks above