In previous versions of ArcGIS Pro, 1.2 and earlier, to use
arcpy, the ArcGIS module for Python, in external scripts, you had to perform a secondary installation. A really handy feature of ArcGIS Pro is autoupdating. When prompted to update Pro from version 1.2 to 1.3, I happily said yes.
Unfortunately, after upgrading I discovered my Python IDE of choice, PyCharm, no longer knew where to find the Python executable. Fortunately I have the luxury of being able to dig up the right person at Esri to tell me how to fix this.
Although there is still a Python34 directory in the
C:\ drive, you will not find
python.exe in here. Rather, you need to configure your IDE to find the executable at
Note: There is a boatload more information and explanations in an article on GeoNet, Python and ArcGIS Pro 1.3: Conda