{"id":417,"date":"2024-01-29T11:00:36","date_gmt":"2024-01-29T11:00:36","guid":{"rendered":"https:\/\/learnpython.elegantwallp.com\/?p=417"},"modified":"2024-01-29T11:00:37","modified_gmt":"2024-01-29T11:00:37","slug":"python-assertalmostequal","status":"publish","type":"post","link":"https:\/\/learnpython.elegantwallp.com\/2024\/01\/29\/python-assertalmostequal\/","title":{"rendered":"Python assertAlmostEqual()"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you learn how to use the Python assertAlmostEqual()<\/code> method to test if two values are approximately equal.<\/p>\n\n\n\n

Introduction to the Python assertAlmostEqual() method<\/h2>\n\n\n\n

The assertAlmostEqual()<\/code> is a method of the TestCase<\/code> class of the unittest<\/code> module. The assertAlmostEqual()<\/code> test if two values are approximately equal by doing the following:<\/p>\n\n\n\n

    \n
  • First, compute the difference.<\/li>\n\n\n\n
  • Second, round to the given number to decimal places (default 7)<\/li>\n\n\n\n
  • Third, compare the rounded value to zero.<\/li>\n<\/ul>\n\n\n\n

    The following shows the syntax of the\u00a0assertAlmostEqual()<\/code>\u00a0method:<\/p>\n\n\n\n

    assertAlmostEqual(first, second, places=7, msg=None, delta=None)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    It uses the following check:<\/p>\n\n\n\n
    round(first-second, 7) == 0<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    The method uses places (or decimal places) to round the difference before comparing it to zero. Note that places are not significant digits.<\/p>\n\n\n\n
    If you pass a delta<\/code> instead of places<\/code> then the difference between first and second must be less or equal to (or greater than) delta.<\/p>\n\n\n\n
    The assertAlmostEqual()<\/code> method allows you to use either places or delta. If you attempt to pass both arguments, you\u2019ll get a TypeError<\/code>.<\/p>\n\n\n\n
    Python assertAlmostEqual method example<\/h2>\n\n\n\n
    First, define a function\u00a0area()<\/code>\u00a0that calculates the area of a circle in the\u00a0circle.py<\/code>\u00a0file:<\/p>\n\n\n\n
    import math def area(radius: float) -> float: return math.pi * math.pow(radius, 2)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    The area()<\/code> function accepts a radius as a float and returns the area of the circle as a float.<\/p>\n\n\n\n
    Since Python can only\u00a0represent floats approximately, you need to use the\u00a0assertAlmostEqual()<\/code>\u00a0method to test the result of the\u00a0area()<\/code>\u00a0with another float.<\/p>\n\n\n\n
    For example, the following test that uses the\u00a0assertEqual()<\/code>\u00a0method will fail:<\/p>\n\n\n\n
    self.assertEqual(0.1+0.1+0.1, 0.3)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    However, the following test that uses the\u00a0assertAlmostEqual()<\/code>\u00a0method will pass:<\/p>\n\n\n\n
    self.assertAlmostEqual(0.1+0.1+0.1, 0.3)<\/code>Code language: Python (python)<\/small><\/p>\n\n\n\n
    Second, define a test module\u00a0test_circle.py<\/code>\u00a0and import the\u00a0circle.py<\/code>\u00a0module:<\/p>\n\n\n\n
    import unittest from circle import area from math import pi class TestCircle(unittest.TestCase): def test_area(self): self.assertAlmostEqual(area(0), 0) self.assertAlmostEqual(area(1), pi) self.assertAlmostEqual(area(0.1), pi*0.1*0.1)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    How it works:<\/p>\n\n\n\n
      \n
    • First, define a TestCircle<\/code> class that inherits the TestCase<\/code> class<\/li>\n\n\n\n
    • Second, add the test_area()<\/code> test method to the TestCircle<\/code> class.<\/li>\n\n\n\n
    • Third, use the assertAlmostEqual()<\/code> method to test if the result of the area()<\/code> function is almost equal to 0<\/code>, pi<\/code>, and pi * 0.1 * 0.1<\/code> .<\/li>\n<\/ul>\n\n\n\n
      Third, run the test:<\/p>\n\n\n\n
      python -m unittest -v<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
      Output:<\/p>\n\n\n\n
      test_area (test_circle.TestCircle) ... ok ---------------------------------------------------------------------- Ran 1 test in 0.000s OK<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
      Python assertNotAlmostEqual() method<\/h2>\n\n\n\n
      The assertNotAlmostEqual()<\/code> method is the opposite of the assertAlmostEqual()<\/code> method. It tests if two values are not approximately equal.<\/p>\n","protected":false},"excerpt":{"rendered":"
      Summary: in this tutorial, you learn how to use the Python assertAlmostEqual() method to test if two values are approximately equal. Introduction to the Python assertAlmostEqual() method The assertAlmostEqual() is a method of the TestCase class of the unittest module. The assertAlmostEqual() test if two values are approximately equal by doing the following: The following shows the syntax of the\u00a0assertAlmostEqual()\u00a0method: It uses the following check: […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[43],"tags":[],"class_list":["post-417","post","type-post","status-publish","format-standard","hentry","category-3-python-unit-testing"],"_links":{"self":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/417","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/comments?post=417"}],"version-history":[{"count":1,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/417\/revisions"}],"predecessor-version":[{"id":418,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/417\/revisions\/418"}],"wp:attachment":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/media?parent=417"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/categories?post=417"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/tags?post=417"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}