Smaller font size of code in code blocks

I want to customize the font size in the code block. For example, in the below picture, I want smaller size of these coding. Is there any way to achieve it by simply adding something in the commonly used markdown for code block? Thanks!

#```python
#```

You must adjust the CSS to your liking. The details might depend on your theme.

One possibility is to use

But that would be on a per block basis.

Else see @chrillek s answer