pip
Downgrade a package to a specific version
For example, I found some runtime error caused by using deprecated APIs. So I decide to downgrade the Scrapy.
First uninstall Scrapy.
$ pip uninstall scrapy
Then install the old version 1.6
$ pip install 'scrapy==1.6'
Collecting scrapy==1.6
...
Installing collected packages: scrapy
Successfully installed scrapy-1.6.0
For more detail when running the command, you could check this post.