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Don't error on piped data #780

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Apr 28, 2024
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5 changes: 5 additions & 0 deletions .github/workflows/ci.yml
Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,11 @@ jobs:
PYTHONIOENCODING: utf-8
PYTHONUTF8: 1
run: pytest --cov agate
- name: Read from stdin
if: matrix.os != 'windows-latest'
run: python -c 'import sys; import agate; agate.Table.from_csv(sys.stdin, sniff_limit=1)' < examples/test.csv
- name: Read from pipe
run: printf 'a,b,c\n1,2,3' | python -c 'import sys; import agate; agate.Table.from_csv(sys.stdin, sniff_limit=1)'
- run: python charts.py
- env:
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
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5 changes: 5 additions & 0 deletions CHANGELOG.rst
Original file line number Diff line number Diff line change
@@ -1,3 +1,8 @@
Unreleased
----------

- fix: Version 1.10.0 errors on piped data.

1.10.1 - April 28, 2024
-----------------------

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24 changes: 17 additions & 7 deletions agate/table/from_csv.py
Original file line number Diff line number Diff line change
@@ -1,5 +1,6 @@
import io
import itertools
from io import StringIO
import sys


@classmethod
Expand Down Expand Up @@ -63,14 +64,23 @@ def from_csv(cls, path, column_names=None, column_types=None, row_names=None, sk

if sniff_limit is None:
# Reads to the end of the tile, but avoid reading the file twice.
handle = StringIO(f.read())
kwargs['dialect'] = csv.Sniffer().sniff(handle.getvalue())
handle = io.StringIO(f.read())
sample = handle.getvalue()
elif sniff_limit > 0:
offset = f.tell()
if f == sys.stdin:
# "At most one single read on the raw stream is done to satisfy the call. The number of bytes returned
# may be less or more than requested." In other words, it reads the buffer_size, which might be less or
# more than the sniff_limit. On my machine, the buffer_size of sys.stdin.buffer is the length of the
# input, up to 65536. This assumes that users don't sniff more than 64 KiB.
# https://docs.python.org/3/library/io.html#io.BufferedReader.peek
sample = sys.stdin.buffer.peek(sniff_limit).decode(encoding, 'ignore')[:sniff_limit] # reads *bytes*
else:
offset = f.tell()
sample = f.read(sniff_limit) # reads *characters*
f.seek(offset) # can't do f.seek(-sniff_limit, os.SEEK_CUR) on file opened in text mode

# Reads only the start of the file.
kwargs['dialect'] = csv.Sniffer().sniff(f.read(sniff_limit))
f.seek(offset)
if sniff_limit is None or sniff_limit > 0:
kwargs['dialect'] = csv.Sniffer().sniff(sample)

reader = csv.reader(handle, header=header, **kwargs)

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1 change: 1 addition & 0 deletions examples/empty.csv
Original file line number Diff line number Diff line change
@@ -0,0 +1 @@

8 changes: 8 additions & 0 deletions tests/test_table/test_from_csv.py
Original file line number Diff line number Diff line change
Expand Up @@ -187,3 +187,11 @@ def test_from_csv_row_limit_too_high(self):
self.assertColumnTypes(table2, [Number, Text, Boolean, Date, DateTime, TimeDelta])

self.assertRows(table2, table1.rows)

def test_from_csv_empty(self):
table = Table.from_csv('examples/empty.csv')

self.assertColumnNames(table, [])
self.assertColumnTypes(table, [])

self.assertRows(table, [])
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