Didn't find this on Google so here it is.
If you are looking for the Interactive Command Prompt when you are debugging for the PyCharm Python IDE Community Edition (the open source free version) go to Tools -> Open Debug Command Line. Somewhat hidden since you would expect it to be under the Debug menu.
Other answers I found told me to click on a non-existent icon on the Debug Toolbar, which either doesn't exist in the Community Edition or was moved / removed.
Hope this helps someone.