Time for action – asserting almost equal

Imagine that you have two numbers that are almost equal. Let's use the assert_almost_equal function to check whether they are equal:

  1. Call the function with low precision (up to seven decimal places):
    print "Decimal 6", np.testing.assert_almost_equal(0.123456789,0.123456780, decimal=7)

    Note that no exception is raised, as you can see in the following result:

    Decimal 6 None
  2. Call the function with higher precision (up to eight decimal places):
    print "Decimal 7", np.testing.assert_almost_equal(0.123456789, 0.123456780, decimal=8)

    The result is:

    Decimal 7
Traceback (most recent call last):
  …
raiseAssertionError(msg)
AssertionError:
Arrays are not almost equal
 ACTUAL: 0.123456789
 DESIRED: 0.12345678

What just happened?

We used the assert_almost_equal function from the NumPy testing package to check whether 0.123456789 and 0.123456780 are equal for different decimal precision.

Pop quiz – specifying decimal precision

Q1. Which parameter of the assert_almost_equal function specifies the decimal precision?

  1. decimal
  2. precision
  3. tolerance
  4. significant
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