FeatureWriter: Option to write to temporary file without giving an explicit path

As a workaround in the meantime, it’s possible to create temporary files in scripted user parameters.

# Parameter Identifier: IN_TEMP_FILE_PATH
import tempfile

# Creates file in FME_TEMP
return tempfile.NamedTemporaryFile(suffix=".parquet", delete=False).name

I’ve not seen this documented anywhere (although I’ve been told that it is intended behavior), but the stock tempfile module has configuration overrides so that the folder its temporary files are created in is the run-specific directory under FME_TEMP. This means that, even if the delete argument is set to false like above, the created file and its parent directory will be deleted when the flow finishes running (or, if caching is enabled in FME Form, whenever the cache is cleared, such as when the next run starts).

This makes such temporary files safe to use between transformers and across your flows without the risk of them not being deleted properly, and without all the issues mentionned above that TempPathnameCreator usually brings.

If you need to break down such paths without the need to use a FilenamePartExtractor, you can also do so in scripted parameters.

# Parameter Identifier: IN_TEMP_FILE_DIR
import os.path

return os.path.dirname(FME_MacroValues['IN_TEMP_FILE_PATH'])

# Parameter Identifier: IN_TEMP_FILE_STEM
import os.path
FILE_SUFFIX = ".parquet"

basename = os.path.basename(FME_MacroValues['IN_TEMP_FILE_PATH'])
assert basename.endswith(FILE_SUFFIX), "{} does not end with {}".format(basename, FILE_SUFFIX)
return basename[:-len(FILE_SUFFIX)]