move approx to own file
This commit is contained in:
Ronny Pfannschmidt
parent
467c526307
commit
36251e0db4
|
|
@ -1265,256 +1265,6 @@ class RaisesContext(object):
|
||||||
return suppress_exception
|
return suppress_exception
|
||||||
|
|
||||||
|
|
||||||
# builtin pytest.approx helper
|
|
||||||
|
|
||||||
class approx(object):
|
|
||||||
"""
|
|
||||||
Assert that two numbers (or two sets of numbers) are equal to each other
|
|
||||||
within some tolerance.
|
|
||||||
|
|
||||||
Due to the `intricacies of floating-point arithmetic`__, numbers that we
|
|
||||||
would intuitively expect to be equal are not always so::
|
|
||||||
|
|
||||||
>>> 0.1 + 0.2 == 0.3
|
|
||||||
False
|
|
||||||
|
|
||||||
__ https://docs.python.org/3/tutorial/floatingpoint.html
|
|
||||||
|
|
||||||
This problem is commonly encountered when writing tests, e.g. when making
|
|
||||||
sure that floating-point values are what you expect them to be. One way to
|
|
||||||
deal with this problem is to assert that two floating-point numbers are
|
|
||||||
equal to within some appropriate tolerance::
|
|
||||||
|
|
||||||
>>> abs((0.1 + 0.2) - 0.3) < 1e-6
|
|
||||||
True
|
|
||||||
|
|
||||||
However, comparisons like this are tedious to write and difficult to
|
|
||||||
understand. Furthermore, absolute comparisons like the one above are
|
|
||||||
usually discouraged because there's no tolerance that works well for all
|
|
||||||
situations. ``1e-6`` is good for numbers around ``1``, but too small for
|
|
||||||
very big numbers and too big for very small ones. It's better to express
|
|
||||||
the tolerance as a fraction of the expected value, but relative comparisons
|
|
||||||
like that are even more difficult to write correctly and concisely.
|
|
||||||
|
|
||||||
The ``approx`` class performs floating-point comparisons using a syntax
|
|
||||||
that's as intuitive as possible::
|
|
||||||
|
|
||||||
>>> from pytest import approx
|
|
||||||
>>> 0.1 + 0.2 == approx(0.3)
|
|
||||||
True
|
|
||||||
|
|
||||||
The same syntax also works on sequences of numbers::
|
|
||||||
|
|
||||||
>>> (0.1 + 0.2, 0.2 + 0.4) == approx((0.3, 0.6))
|
|
||||||
True
|
|
||||||
|
|
||||||
By default, ``approx`` considers numbers within a relative tolerance of
|
|
||||||
``1e-6`` (i.e. one part in a million) of its expected value to be equal.
|
|
||||||
This treatment would lead to surprising results if the expected value was
|
|
||||||
``0.0``, because nothing but ``0.0`` itself is relatively close to ``0.0``.
|
|
||||||
To handle this case less surprisingly, ``approx`` also considers numbers
|
|
||||||
within an absolute tolerance of ``1e-12`` of its expected value to be
|
|
||||||
equal. Infinite numbers are another special case. They are only
|
|
||||||
considered equal to themselves, regardless of the relative tolerance. Both
|
|
||||||
the relative and absolute tolerances can be changed by passing arguments to
|
|
||||||
the ``approx`` constructor::
|
|
||||||
|
|
||||||
>>> 1.0001 == approx(1)
|
|
||||||
False
|
|
||||||
>>> 1.0001 == approx(1, rel=1e-3)
|
|
||||||
True
|
|
||||||
>>> 1.0001 == approx(1, abs=1e-3)
|
|
||||||
True
|
|
||||||
|
|
||||||
If you specify ``abs`` but not ``rel``, the comparison will not consider
|
|
||||||
the relative tolerance at all. In other words, two numbers that are within
|
|
||||||
the default relative tolerance of ``1e-6`` will still be considered unequal
|
|
||||||
if they exceed the specified absolute tolerance. If you specify both
|
|
||||||
``abs`` and ``rel``, the numbers will be considered equal if either
|
|
||||||
tolerance is met::
|
|
||||||
|
|
||||||
>>> 1 + 1e-8 == approx(1)
|
|
||||||
True
|
|
||||||
>>> 1 + 1e-8 == approx(1, abs=1e-12)
|
|
||||||
False
|
|
||||||
>>> 1 + 1e-8 == approx(1, rel=1e-6, abs=1e-12)
|
|
||||||
True
|
|
||||||
|
|
||||||
If you're thinking about using ``approx``, then you might want to know how
|
|
||||||
it compares to other good ways of comparing floating-point numbers. All of
|
|
||||||
these algorithms are based on relative and absolute tolerances and should
|
|
||||||
agree for the most part, but they do have meaningful differences:
|
|
||||||
|
|
||||||
- ``math.isclose(a, b, rel_tol=1e-9, abs_tol=0.0)``: True if the relative
|
|
||||||
tolerance is met w.r.t. either ``a`` or ``b`` or if the absolute
|
|
||||||
tolerance is met. Because the relative tolerance is calculated w.r.t.
|
|
||||||
both ``a`` and ``b``, this test is symmetric (i.e. neither ``a`` nor
|
|
||||||
``b`` is a "reference value"). You have to specify an absolute tolerance
|
|
||||||
if you want to compare to ``0.0`` because there is no tolerance by
|
|
||||||
default. Only available in python>=3.5. `More information...`__
|
|
||||||
|
|
||||||
__ https://docs.python.org/3/library/math.html#math.isclose
|
|
||||||
|
|
||||||
- ``numpy.isclose(a, b, rtol=1e-5, atol=1e-8)``: True if the difference
|
|
||||||
between ``a`` and ``b`` is less that the sum of the relative tolerance
|
|
||||||
w.r.t. ``b`` and the absolute tolerance. Because the relative tolerance
|
|
||||||
is only calculated w.r.t. ``b``, this test is asymmetric and you can
|
|
||||||
think of ``b`` as the reference value. Support for comparing sequences
|
|
||||||
is provided by ``numpy.allclose``. `More information...`__
|
|
||||||
|
|
||||||
__ http://docs.scipy.org/doc/numpy-1.10.0/reference/generated/numpy.isclose.html
|
|
||||||
|
|
||||||
- ``unittest.TestCase.assertAlmostEqual(a, b)``: True if ``a`` and ``b``
|
|
||||||
are within an absolute tolerance of ``1e-7``. No relative tolerance is
|
|
||||||
considered and the absolute tolerance cannot be changed, so this function
|
|
||||||
is not appropriate for very large or very small numbers. Also, it's only
|
|
||||||
available in subclasses of ``unittest.TestCase`` and it's ugly because it
|
|
||||||
doesn't follow PEP8. `More information...`__
|
|
||||||
|
|
||||||
__ https://docs.python.org/3/library/unittest.html#unittest.TestCase.assertAlmostEqual
|
|
||||||
|
|
||||||
- ``a == pytest.approx(b, rel=1e-6, abs=1e-12)``: True if the relative
|
|
||||||
tolerance is met w.r.t. ``b`` or if the absolute tolerance is met.
|
|
||||||
Because the relative tolerance is only calculated w.r.t. ``b``, this test
|
|
||||||
is asymmetric and you can think of ``b`` as the reference value. In the
|
|
||||||
special case that you explicitly specify an absolute tolerance but not a
|
|
||||||
relative tolerance, only the absolute tolerance is considered.
|
|
||||||
"""
|
|
||||||
|
|
||||||
def __init__(self, expected, rel=None, abs=None):
|
|
||||||
self.expected = expected
|
|
||||||
self.abs = abs
|
|
||||||
self.rel = rel
|
|
||||||
|
|
||||||
def __repr__(self):
|
|
||||||
return ', '.join(repr(x) for x in self.expected)
|
|
||||||
|
|
||||||
def __eq__(self, actual):
|
|
||||||
from collections import Iterable
|
|
||||||
if not isinstance(actual, Iterable):
|
|
||||||
actual = [actual]
|
|
||||||
if len(actual) != len(self.expected):
|
|
||||||
return False
|
|
||||||
return all(a == x for a, x in zip(actual, self.expected))
|
|
||||||
|
|
||||||
__hash__ = None
|
|
||||||
|
|
||||||
def __ne__(self, actual):
|
|
||||||
return not (actual == self)
|
|
||||||
|
|
||||||
@property
|
|
||||||
def expected(self):
|
|
||||||
# Regardless of whether the user-specified expected value is a number
|
|
||||||
# or a sequence of numbers, return a list of ApproxNotIterable objects
|
|
||||||
# that can be compared against.
|
|
||||||
from collections import Iterable
|
|
||||||
approx_non_iter = lambda x: ApproxNonIterable(x, self.rel, self.abs)
|
|
||||||
if isinstance(self._expected, Iterable):
|
|
||||||
return [approx_non_iter(x) for x in self._expected]
|
|
||||||
else:
|
|
||||||
return [approx_non_iter(self._expected)]
|
|
||||||
|
|
||||||
@expected.setter
|
|
||||||
def expected(self, expected):
|
|
||||||
self._expected = expected
|
|
||||||
|
|
||||||
|
|
||||||
class ApproxNonIterable(object):
|
|
||||||
"""
|
|
||||||
Perform approximate comparisons for single numbers only.
|
|
||||||
|
|
||||||
In other words, the ``expected`` attribute for objects of this class must
|
|
||||||
be some sort of number. This is in contrast to the ``approx`` class, where
|
|
||||||
the ``expected`` attribute can either be a number of a sequence of numbers.
|
|
||||||
This class is responsible for making comparisons, while ``approx`` is
|
|
||||||
responsible for abstracting the difference between numbers and sequences of
|
|
||||||
numbers. Although this class can stand on its own, it's only meant to be
|
|
||||||
used within ``approx``.
|
|
||||||
"""
|
|
||||||
|
|
||||||
def __init__(self, expected, rel=None, abs=None):
|
|
||||||
self.expected = expected
|
|
||||||
self.abs = abs
|
|
||||||
self.rel = rel
|
|
||||||
|
|
||||||
def __repr__(self):
|
|
||||||
if isinstance(self.expected, complex):
|
|
||||||
return str(self.expected)
|
|
||||||
|
|
||||||
# Infinities aren't compared using tolerances, so don't show a
|
|
||||||
# tolerance.
|
|
||||||
if math.isinf(self.expected):
|
|
||||||
return str(self.expected)
|
|
||||||
|
|
||||||
# If a sensible tolerance can't be calculated, self.tolerance will
|
|
||||||
# raise a ValueError. In this case, display '???'.
|
|
||||||
try:
|
|
||||||
vetted_tolerance = '{:.1e}'.format(self.tolerance)
|
|
||||||
except ValueError:
|
|
||||||
vetted_tolerance = '???'
|
|
||||||
|
|
||||||
if sys.version_info[0] == 2:
|
|
||||||
return '{0} +- {1}'.format(self.expected, vetted_tolerance)
|
|
||||||
else:
|
|
||||||
return u'{0} \u00b1 {1}'.format(self.expected, vetted_tolerance)
|
|
||||||
|
|
||||||
def __eq__(self, actual):
|
|
||||||
# Short-circuit exact equality.
|
|
||||||
if actual == self.expected:
|
|
||||||
return True
|
|
||||||
|
|
||||||
# Infinity shouldn't be approximately equal to anything but itself, but
|
|
||||||
# if there's a relative tolerance, it will be infinite and infinity
|
|
||||||
# will seem approximately equal to everything. The equal-to-itself
|
|
||||||
# case would have been short circuited above, so here we can just
|
|
||||||
# return false if the expected value is infinite. The abs() call is
|
|
||||||
# for compatibility with complex numbers.
|
|
||||||
if math.isinf(abs(self.expected)):
|
|
||||||
return False
|
|
||||||
|
|
||||||
# Return true if the two numbers are within the tolerance.
|
|
||||||
return abs(self.expected - actual) <= self.tolerance
|
|
||||||
|
|
||||||
__hash__ = None
|
|
||||||
|
|
||||||
def __ne__(self, actual):
|
|
||||||
return not (actual == self)
|
|
||||||
|
|
||||||
@property
|
|
||||||
def tolerance(self):
|
|
||||||
set_default = lambda x, default: x if x is not None else default
|
|
||||||
|
|
||||||
# Figure out what the absolute tolerance should be. ``self.abs`` is
|
|
||||||
# either None or a value specified by the user.
|
|
||||||
absolute_tolerance = set_default(self.abs, 1e-12)
|
|
||||||
|
|
||||||
if absolute_tolerance < 0:
|
|
||||||
raise ValueError("absolute tolerance can't be negative: {}".format(absolute_tolerance))
|
|
||||||
if math.isnan(absolute_tolerance):
|
|
||||||
raise ValueError("absolute tolerance can't be NaN.")
|
|
||||||
|
|
||||||
# If the user specified an absolute tolerance but not a relative one,
|
|
||||||
# just return the absolute tolerance.
|
|
||||||
if self.rel is None:
|
|
||||||
if self.abs is not None:
|
|
||||||
return absolute_tolerance
|
|
||||||
|
|
||||||
# Figure out what the relative tolerance should be. ``self.rel`` is
|
|
||||||
# either None or a value specified by the user. This is done after
|
|
||||||
# we've made sure the user didn't ask for an absolute tolerance only,
|
|
||||||
# because we don't want to raise errors about the relative tolerance if
|
|
||||||
# we aren't even going to use it.
|
|
||||||
relative_tolerance = set_default(self.rel, 1e-6) * abs(self.expected)
|
|
||||||
|
|
||||||
if relative_tolerance < 0:
|
|
||||||
raise ValueError("relative tolerance can't be negative: {}".format(absolute_tolerance))
|
|
||||||
if math.isnan(relative_tolerance):
|
|
||||||
raise ValueError("relative tolerance can't be NaN.")
|
|
||||||
|
|
||||||
# Return the larger of the relative and absolute tolerances.
|
|
||||||
return max(relative_tolerance, absolute_tolerance)
|
|
||||||
|
|
||||||
|
|
||||||
#
|
#
|
||||||
# the basic pytest Function item
|
# the basic pytest Function item
|
||||||
#
|
#
|
||||||
|
|
|
||||||
|
|
@ -22,10 +22,12 @@ from _pytest.skipping import xfail
|
||||||
from _pytest.main import Item, Collector, File, Session
|
from _pytest.main import Item, Collector, File, Session
|
||||||
from _pytest.fixtures import fillfixtures as _fillfuncargs
|
from _pytest.fixtures import fillfixtures as _fillfuncargs
|
||||||
from _pytest.python import (
|
from _pytest.python import (
|
||||||
raises, approx,
|
raises,
|
||||||
Module, Class, Instance, Function, Generator,
|
Module, Class, Instance, Function, Generator,
|
||||||
)
|
)
|
||||||
|
|
||||||
|
from _pytest.python_api import approx
|
||||||
|
|
||||||
set_trace = __pytestPDB.set_trace
|
set_trace = __pytestPDB.set_trace
|
||||||
|
|
||||||
__all__ = [
|
__all__ = [
|
||||||
|
|
|
||||||
Loading…
Reference in New Issue