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FIX: _safe_first_finite on all non-finite array #25547

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Merged
merged 1 commit into from
May 12, 2023
+17 −13
Merged

FIX: _safe_first_finite on all non-finite array #25547

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8 changes: 0 additions & 8 deletions lib/matplotlib/axes/_axes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2208,19 +2208,11 @@ def _convert_dx(dx, x0, xconv, convert):
x0 = cbook._safe_first_finite(x0)
except (TypeError, IndexError, KeyError):
pass
except StopIteration:
# this means we found no finite element, fall back to first
# element unconditionally
x0 = cbook.safe_first_element(x0)

try:
x = cbook._safe_first_finite(xconv)
except (TypeError, IndexError, KeyError):
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I think there a few other places where StopIteration is try/excepted for _safe_first_element? Did you check all those?

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I hadn't, but I have now. I only found these two:

matplotlib/lib/matplotlib/dates.py

Lines 1828 to 1831 in 7103779

try:
x = cbook._safe_first_finite(x)
except (TypeError, StopIteration):
pass

matplotlib/lib/matplotlib/units.py

Lines 182 to 185 in 7103779

try: # If cache lookup fails, look up based on first element...
first = cbook._safe_first_finite(x)
except (TypeError, StopIteration):
pass

These both predate the change that led to StopIteration being thrown for all-nan arrays. The commit that introduced the first says it was for zero length objects, and these will still trigger a StopIteration when the logic arrives here. I'm not sure about the second - should units.Registry.get_converter also be able to handle zero length objects?

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I don't really know - just noted that it happens a few other places, and the more logic we can move into a consistent helper function, the better in my opinion.

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the more logic we can move into a consistent helper function, the better in my opinion.

I certainly agree with that. I wonder if further consolidation should wait for a separate PR though, given recent clarifications about what should and should not be backported

  • my current change fixes a regression from v3.6, so it would be good to get in a patch release
  • a change that tidies the code but (hopefully) makes no difference to the user should maybe wait till v3.8

x = xconv
except StopIteration:
# this means we found no finite element, fall back to first
# element unconditionally
x = cbook.safe_first_element(xconv)

delist = False
if not np.iterable(dx):
Expand Down
10 changes: 5 additions & 5 deletions lib/matplotlib/cbook.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1619,13 +1619,13 @@ def safe_first_element(obj):

def _safe_first_finite(obj, *, skip_nonfinite=True):
"""
Return the first non-None (and optionally finite) element in *obj*.
Return the first finite element in *obj* if one is available and skip_nonfinite is
True. Otherwise return the first element.

This is a method for internal use.

This is a type-independent way of obtaining the first non-None element,
supporting both index access and the iterator protocol.
The first non-None element will be obtained when skip_none is True.
This is a type-independent way of obtaining the first finite element, supporting
both index access and the iterator protocol.
"""
def safe_isfinite(val):
if val is None:
Expand Down Expand Up @@ -1657,7 +1657,7 @@ def safe_isfinite(val):
raise RuntimeError("matplotlib does not "
"support generators as input")
else:
return next(val for val in obj if safe_isfinite(val))
return next((val for val in obj if safe_isfinite(val)), safe_first_element(obj))


def sanitize_sequence(data):
Expand Down
12 changes: 12 additions & 0 deletions lib/matplotlib/tests/test_cbook.py
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Expand Up @@ -608,6 +608,18 @@ def test_flatiter():
assert 1 == next(it)


def test__safe_first_finite_all_nan():
arr = np.full(2, np.nan)
ret = cbook._safe_first_finite(arr)
assert np.isnan(ret)


def test__safe_first_finite_all_inf():
arr = np.full(2, np.inf)
ret = cbook._safe_first_finite(arr)
assert np.isinf(ret)


def test_reshape2d():

class Dummy:
Expand Down