PyCharm and IntelliJ both have "Community Editions" that are free, but missing a few features. They're very usable in that state. Something else to note is that

PyCharm and IntelliJ both have "Community Editions" that are free, but missing a few features. They're very usable in that state. Something else to note is that Android Studio, which is similarly free to use, is based on IntelliJ CE.