At some point pyproj used classmethods for constructor-type methods in pyproj.crs.CRS. In this commit this was changed to use staticmethods. The linked issue does not seem to mention this change (unless I missed it). In any case, this change effectively breaks subclassing, as in this example:

import pyproj


class myCRS(pyproj.crs.CRS):
    def print_foo(self):
        print("foo-bar!")


proj = pyproj.Proj("+proj=etmerc +ellps=GRS80 +lon_0=13 +lat_0=2 +x_0=0 +y_0=0 +k_0=1")
crs = myCRS.from_proj4(proj.definition_string())
print(type(crs))
print(isinstance(crs, myCRS))
crs.print_foo()

Expected Output

expect:

<class '__main__.myCRS'>
True
foo-bar!

what you get:

<class 'pyproj.crs.crs.CRS'>
False
...
AttributeError: 'CRS' object has no attribute 'print_foo'

Environment Information

Any ( we had been using pyproj v2.4.1, and just upgraded to 3.0.1)

Installation method

build from source