---
id: practical-python-1.15
source_exercise_id: "1.15"
title: "Membership testing (substring testing)"
section: "1.4 Strings"
source_path: "01_Introduction/04_Strings.md"
source_repo: "https://github.com/dabeaz-course/practical-python"
source_commit: "93dca856b41c61a0a0f85ae334116e4c125629ea"
student_visible_solution: false
has_private_solution: false
skip: false
---

# Exercise 1.15: Membership testing (substring testing)

> Source: Practical Python Programming, `01_Introduction/04_Strings.md`.

### Exercise 1.15: Membership testing (substring testing)

Experiment with the `in` operator to check for substrings.  At the
interactive prompt, try these operations:

```python
>>> 'IBM' in symbols
?
>>> 'AA' in symbols
True
>>> 'CAT' in symbols
?
>>>
```

*Why did the check for `'AA'` return `True`?*

## 关联来源

- [[summaries/04_Strings]]