The +init= syntax is deprecated. So all you need is the ESRI:102001 part. See: https://pyproj4.github.io/pyproj/stable/gotchas.html#init-auth-auth-code-should-be-replaced-with-auth-auth-code
inputGDF.crs = 'esri:102001'
The issue you are having is due to axis order changes in PROJ 6+: https://pyproj4.github.io/pyproj/stable/gotchas.html#axis-order-changes-in-proj-6
One solution is to use always_xy:
from shapely.geometry import LineString
from shapely.ops import transform
from functools import partial
roadsegment = LineString([(5.318945751388698, 50....
You need to set the environment variables to run the QGIS python outside.
In this case my QGIS installation is in D:\QGIS, so you should only change OSGEO4W_ROOT.
@jelleve, your answer is correct and in line with https://pyproj4.github.io/pyproj/stable/advanced_examples.html#optimize-transformations.
Additionally, you may be interested in geopandas. It will enable you to read/write these geometries and reproject them using the same method you showed above using one line of code:
gdf = geopandas.read_file("input....
After some experimenting, it seems that I was just plain wrong. My initial code looked as follows:
transformer = pyproj.Transformer.from_proj(pyproj.Proj(init='epsg:27563'), pyproj.Proj(init='epsg:4326'))
projected = shapely.ops.transform(transformer.transform, polygon)
for polygon in polygons: