I cannot seem to be able to find the setting to enable line numbers for all files, but I have to always right click and enable this on per file basis.
There mu
PyCharm Version 3.4.1(For all files in the project):
File -> Preferences -> Editor (IDE Settings) -> Appearance -> mark 'Show line numbers'
PyCharm Version 3.4.1(only for existing file in the project):
View -> Active Editor -> Show Line Numbers