GeoJSONSeq append to file

Expected behavior and actual behavior.

Appending to a GeoJSON newline-delimited file is not currently supported.

https://github.com/Toblerity/Fiona/blob/2ec38d087fea72c8bd0e7696d8ac1a6203df8851/fiona/drvsupport.py#L54

I can’t find any other issues mentioning appending using GeoJSONSeq, and given the nature of the format, it seems like that should be possible. Where would a PR to enable that take place?

Steps to reproduce the problem.

import fiona
import geopandas as gpd
from geopandas.io.file import infer_schema
from shapely.geometry import Point

gdf = gpd.GeoDataFrame(geometry=[Point([0, 1])])
schema = infer_schema(gdf)
with fiona.open('test.geojson', "w", driver='GeoJSONSeq', schema=schema) as colxn:
    colxn.writerecords(gdf.iterfeatures())

gdf = gpd.GeoDataFrame(geometry=[Point([2, 2])])
schema = infer_schema(gdf)
with fiona.open('test.geojson', "a", driver='GeoJSONSeq', schema=schema) as colxn:
    colxn.writerecords(gdf.iterfeatures())

---------------------------------------------------------------------------
DriverError                               Traceback (most recent call last)
<ipython-input-26-01e338412202> in <module>
----> 1 with fiona.open('test.geojson', "a", driver='GeoJSONSeq', schema=schema) as colxn:
      2 
      3     colxn.writerecords(gdf.iterfeatures())
      4 

~/local/anaconda3/envs/create-database/lib/python3.7/site-packages/fiona/env.py in wrapper(*args, **kwargs)
    405             with Env.from_defaults(session=session):
    406                 log.debug("Credentialized: {!r}".format(getenv()))
--> 407                 return f(*args, **kwargs)
    408     return wrapper
    409 

~/local/anaconda3/envs/create-database/lib/python3.7/site-packages/fiona/__init__.py in open(fp, mode, driver, schema, crs, encoding, layer, vfs, enabled_drivers, crs_wkt, **kwargs)
    252         if mode in ('a', 'r'):
    253             c = Collection(path, mode, driver=driver, encoding=encoding,
--> 254                            layer=layer, enabled_drivers=enabled_drivers, **kwargs)
    255         elif mode == 'w':
    256             if schema:

~/local/anaconda3/envs/create-database/lib/python3.7/site-packages/fiona/collection.py in __init__(self, path, mode, driver, schema, crs, encoding, layer, vsi, archive, enabled_drivers, crs_wkt, ignore_fields, ignore_geometry, **kwargs)
    161 
    162         if self.session is not None:
--> 163             self.guard_driver_mode()
    164 
    165         if self.mode in ("a", "w"):

~/local/anaconda3/envs/create-database/lib/python3.7/site-packages/fiona/collection.py in guard_driver_mode(self)
    180             raise DriverError("unsupported driver: %r" % driver)
    181         if self.mode not in supported_drivers[driver]:
--> 182             raise DriverError("unsupported mode: %r" % self.mode)
    183 
    184     @property

DriverError: unsupported mode: 'a'

Operating system

For example: Mac OS X 10.15.1

Fiona and GDAL version and provenance

Fiona 1.8.11, from Conda Gdal 3.0.2, from Conda

[sgillies]

@kannes thank you. This not good: the raison d’être for GeoJSON sequences is to allow incremental parsing and appending. It’s not a write once format.

[kylebarron]

Yeah, agreed. I’m a little surprised it wasn’t supported by default when the functionality was added. I don’t know C/C++ or else I’d try to make a PR to GDAL. In any case, I’ll see what responses I get on the GDAL issue, linked above.