diff options
Diffstat (limited to 'numpy/lib')
| -rw-r--r-- | numpy/lib/npyio.py | 24 | ||||
| -rw-r--r-- | numpy/lib/tests/test_io.py | 54 |
2 files changed, 75 insertions, 3 deletions
diff --git a/numpy/lib/npyio.py b/numpy/lib/npyio.py index 9d539d6ac..2e68979c4 100644 --- a/numpy/lib/npyio.py +++ b/numpy/lib/npyio.py @@ -1204,7 +1204,8 @@ def genfromtxt(fname, dtype=float, comments='#', delimiter=None, usecols=None, names=None, excludelist=None, deletechars=None, replace_space='_', autostrip=False, case_sensitive=True, defaultfmt="f%i", - unpack=None, usemask=False, loose=True, invalid_raise=True): + unpack=None, usemask=False, loose=True, invalid_raise=True, + max_rows=None): """ Load data from a text file, with missing values handled as specified. @@ -1285,6 +1286,12 @@ def genfromtxt(fname, dtype=float, comments='#', delimiter=None, If True, an exception is raised if an inconsistency is detected in the number of columns. If False, a warning is emitted and the offending lines are skipped. + max_rows : int, optional + The maximum number of rows to read. Must not be used with skip_footer + at the same time. If given, the value must be at least 1. Default is + to read the entire file. + + .. versionadded:: 1.10.0 Returns ------- @@ -1353,6 +1360,14 @@ def genfromtxt(fname, dtype=float, comments='#', delimiter=None, dtype=[('intvar', '<i8'), ('fltvar', '<f8'), ('strvar', '|S5')]) """ + if max_rows is not None: + if skip_footer: + raise ValueError( + "The keywords 'skip_footer' and 'max_rows' can not be " + "specified at the same time.") + if max_rows < 1: + raise ValueError("'max_rows' must be at least 1.") + # Py3 data conversions to bytes, for convenience if comments is not None: comments = asbytes(comments) @@ -1647,8 +1662,8 @@ def genfromtxt(fname, dtype=float, comments='#', delimiter=None, # Skip an empty line if nbvalues == 0: continue - # Select only the columns we need if usecols: + # Select only the columns we need try: values = [values[_] for _ in usecols] except IndexError: @@ -1661,7 +1676,10 @@ def genfromtxt(fname, dtype=float, comments='#', delimiter=None, append_to_rows(tuple(values)) if usemask: append_to_masks(tuple([v.strip() in m - for (v, m) in zip(values, missing_values)])) + for (v, m) in zip(values, + missing_values)])) + if len(rows) == max_rows: + break if own_fhd: fhd.close() diff --git a/numpy/lib/tests/test_io.py b/numpy/lib/tests/test_io.py index 81bddfadd..2ce78575b 100644 --- a/numpy/lib/tests/test_io.py +++ b/numpy/lib/tests/test_io.py @@ -1641,6 +1641,60 @@ M 33 21.99 self.assertTrue(isinstance(test, np.recarray)) assert_equal(test, control) + def test_max_rows(self): + # Test the `max_rows` keyword argument. + data = '1 2\n3 4\n5 6\n7 8\n9 10\n' + txt = TextIO(data) + a1 = np.genfromtxt(txt, max_rows=3) + a2 = np.genfromtxt(txt) + assert_equal(a1, [[1, 2], [3, 4], [5, 6]]) + assert_equal(a2, [[7, 8], [9, 10]]) + + # max_rows must be at least 1. + assert_raises(ValueError, np.genfromtxt, TextIO(data), max_rows=0) + + # An input with several invalid rows. + data = '1 1\n2 2\n0 \n3 3\n4 4\n5 \n6 \n7 \n' + + test = np.genfromtxt(TextIO(data), max_rows=2) + control = np.array([[1., 1.], [2., 2.]]) + assert_equal(test, control) + + # Test keywords conflict + assert_raises(ValueError, np.genfromtxt, TextIO(data), skip_footer=1, + max_rows=4) + + # Test with invalid value + assert_raises(ValueError, np.genfromtxt, TextIO(data), max_rows=4) + + # Test with invalid not raise + with warnings.catch_warnings(): + warnings.filterwarnings("ignore") + + test = np.genfromtxt(TextIO(data), max_rows=4, invalid_raise=False) + control = np.array([[1., 1.], [2., 2.], [3., 3.], [4., 4.]]) + assert_equal(test, control) + + test = np.genfromtxt(TextIO(data), max_rows=5, invalid_raise=False) + control = np.array([[1., 1.], [2., 2.], [3., 3.], [4., 4.]]) + assert_equal(test, control) + + # Structured array with field names. + data = 'a b\n#c d\n1 1\n2 2\n#0 \n3 3\n4 4\n5 5\n' + + # Test with header, names and comments + txt = TextIO(data) + test = np.genfromtxt(txt, skip_header=1, max_rows=3, names=True) + control = np.array([(1.0, 1.0), (2.0, 2.0), (3.0, 3.0)], + dtype=[('c', '<f8'), ('d', '<f8')]) + assert_equal(test, control) + # To continue reading the same "file", don't use skip_header or + # names, and use the previously determined dtype. + test = np.genfromtxt(txt, max_rows=None, dtype=test.dtype) + control = np.array([(4.0, 4.0), (5.0, 5.0)], + dtype=[('c', '<f8'), ('d', '<f8')]) + assert_equal(test, control) + def test_gft_using_filename(self): # Test that we can load data from a filename as well as a file object wanted = np.arange(6).reshape((2, 3)) |