Buffer crashes: ValueError: No Shapely geometry can be created from null value

Expected behavior and actual behavior.

I encountered “ValueError: No Shapely geometry can be created from null value” when I tried to get the buffer area of a sequence of locations (represented as pair of [grid_x, grid_y]).

Steps to reproduce the problem.

(For example, a script with required data) Here is the link of test input. test.csv And error happens after running the following script. df = pd.read_csv("test.csv") grid_path = df.loc[:, ['grid_x','grid_y']].values.tolist() path = LineString(grid_path) print("path is valid?", path.is_valid) buffer_path = path.buffer(2, cap_style=1)

Operating system

Mac OS X 10.13.6

Shapely version and provenance

I used 1.6.4. post 2 from PyPI using pip

Thank you for any help!

[sgillies]

I’m happy to see that there is not an actual crashing bug here: you can recover from an exception, but not from a true crash.

@jGaboardi thanks for your help! Nodes that are very close to each other, closer than our computers’ precision, are a problem for some of the algorithms in GEOS. Simplifying geometries has helped in some cases.

@RuiR I’m happy to look into this and even to take it upstream to GEOS if needed, but I need a less complicated example to see if I can reproduce the problem. Can you paste here a representation (WKT, for example) of a geometry that can’t be buffered?

[RuiR]

As @jGaboardi suggested, I buffered each segment path and dissolve all buffer using cascaded_union imported from shapely.ops. This works fine and runs quickly.

But the result is not the same with the previous method (buffering the long LineString of the whole path). I’m curious about the process of buffering the whole path.