FutureWarning:Use of pyproj.transform is deprecated since pyproj>2.6.1

[philippkraft]

Hi,

thank you for the great package. When running pysheds 0.3.3 with pyproj 3.4.1 I get a warning:

pysheds/sview.py:971: FutureWarning: This function is deprecated. See: https://pyproj4.github.io/pyproj/stable/gotchas.html#upgrading-to-pyproj-2-from-pyproj-1

According to the documentation of pyproj.transform calling this function is deprecated since pyproj 2.6.1. To fix it one need to change pysheds/sview.py:971 and all other occurences to something like:

transformer = pyproj.Transformer.from_proj(target_view.crs, data_view.crs, always_xy=True)
xt, yt = transformer.transform(x=x, y=y, errcheck=True)

I have not tested it yet. This is also necessary for all other occurences of pyproj.transform:

pysheds/pysheds/io.py

Lines 117 to 119 in 9d96096

	extent = pyproj.transform(window_crs, crs, (xmin, xmax),
	(ymin, ymax), errcheck=True,
	always_xy=True)

pysheds/pysheds/pgrid.py

Lines 292 to 294 in 3b977e8

	extent = pyproj.transform(window_crs, crs, (xmin, xmax),
	(ymin, ymax), errcheck=True,
	always_xy=True)

pysheds/pysheds/sview.py

Lines 237 to 238 in 1951f63

	xb_p, yb_p = pyproj.transform(old_crs, new_crs, xb, yb,
	errcheck=True, always_xy=True)

And of course the original one:

pysheds/pysheds/sview.py

Lines 971 to 972 in 1951f63

	xt, yt = pyproj.transform(target_view.crs, data_view.crs, x=x, y=y,
	errcheck=True, always_xy=True)

I can submit a PR, if it helps.

Regards, Philipp

[philippkraft]

@mdbartos I would suggest the following refactoring:

Move all duplicated pyproj helper code (_OLD_PYPROJ and _pyproj_init) in a seperated python module (projection.py). In that file, the default projection is defined as well as a function for transformation, which is called instead of pyproj.transform and has the same interface. For old pyproj (<2.6.1), the function just calls pyproj.transform (as now) for newer pyproj the function first creates an transformer object and calls it with the provided data.

[philippkraft]

Another question: is support for pyproj<2.2 (relase 04/2019) still necessary?