Fix IndexError in _read_rdb when NWIS returns no data rows#227
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thodson-usgs merged 2 commits intoDOI-USGS:mainfrom Apr 13, 2026
Merged
Fix IndexError in _read_rdb when NWIS returns no data rows#227thodson-usgs merged 2 commits intoDOI-USGS:mainfrom
thodson-usgs merged 2 commits intoDOI-USGS:mainfrom
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When an NWIS service responds with only comment lines (e.g. "No sites found matching all criteria"), _read_rdb tried to index past the end of the lines list and raised an unhelpful IndexError. Now it detects the empty-data case, extracts the Response-Message from the comment block, and raises a ValueError with that message instead. Fixes DOI-USGS#171. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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When the NWIS service responds with only comment lines (e.g. "No sites found matching all criteria"), _read_rdb indexed past the end of the line list and raised an unhelpful IndexError. Since this is a legitimate empty result rather than an error, the fix returns an empty DataFrame so callers can use the idiomatic df.empty check instead of catching an exception. Fixes DOI-USGS#171. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
Fixes #171.
When the NWIS stats service has no data for a site, it returns a valid HTTP 200 with only comment lines:
_read_rdbtried to indexlines[count]for field names after counting comment lines, but with no data rowscount == len(lines), causing an unhelpfulIndexError.Since this is a legitimate empty result (not an error), the fix returns an empty
DataFrameso callers can use the idiomaticdf.emptycheck:Test plan
TestReadRdb::test_no_sites_returns_empty_dataframe— uses the exact response body from the live endpoint (https://waterservices.usgs.gov/nwis/stat/?sites=02469675)TestReadRdb::test_all_comments_returns_empty_dataframe— generic all-comments caseTestReadRdb::test_valid_rdb_returns_dataframe— regression: normal responses still parse correctlytests/nwis_test.pysuite passes (30/30)🤖 Generated with Claude Code