I want to scrape a webpage that changes its content via a <select> tag. When I select a different option, the content of the page dynamically changes. I want to know if there is a way that I can change the option from a python script so I can get the content from all different pages of all different options in <select> tag.
As @Tichodroma said, when the select is changed, either:

Some content previously hidden on the page is made visible, or:
An ajax call is made to retrieve some additional content and add it to the DOM

In both cases, JavaScript is involved. Have a look at it, and depending on what is happening (case #1 or #2), you should:

Scrape the whole page, since all the content you want is already in it, or:
Make several calls to the file usually called using ajax to retrieve the content you want for each value of the <select>
How to scrape a webpage that changes content from  tag