# Python unittest – assertAlmostEqual() function

• Last Updated : 29 Aug, 2020

assertAlmostEqual() in Python is a unittest library function that is used in unit testing to check whether two given values are almost equal or not. This function will take five parameters as input and return a boolean value depending upon the assert condition.

This function check that first and second are approximately equal by computing the difference, rounding to the given number of decimal places (default 7), and comparing to zero.

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If delta is supplied instead of places then the difference between first and second must be less or equal to delta.

Syntax: assertAlmostEqual(first, second, places=7, message=None, delta=None)

Parameters: assertAlmostEqual() accept three parameters which are listed below with explanation:

• first: first input value (integer)
• second:  second input value (integer)
• places: decimal places for approximation
• message: a string sentence as a message which got displayed when the test case got failed.
• delta: delta value for approximation

Listed below are two different examples illustrating the positive and negative test case for given assert function:

Example :

## Python3

 `# test suite``import` `unittest`` ` ` ` `class` `TestStringMethods(unittest.TestCase):``    ``# negative test function to test if values are almost equal with place``    ``def` `test_negativeWithPlaces(``self``):``        ``first ``=` `4.4555``        ``second ``=` `4.4566``        ``decimalPlace ``=` `3``        ``# error message in case if test case got failed``        ``message ``=` `"first and second are not almost equal."``        ``# assert function() to check if values are almost equal``        ``self``.assertAlmostEqual(first, second, decimalPlace, message)`` ` `    ``# positive test function to test if values are almost equal with place``    ``def` `test_positiveWithPlaces(``self``):``        ``first ``=` `4.4555``        ``second ``=` `4.4566``        ``decimalPlace ``=` `2``        ``# error message in case if test case got failed``        ``message ``=` `"first and second are not almost equal."``        ``# assert function() to check if values are almost equal``        ``self``.assertAlmostEqual(first, second, decimalPlace, message)`` ` `    ``# negative test function to test if values are almost equal with delta``    ``def` `test_negativeWithDelta(``self``):``        ``first ``=` `4.4555``        ``second ``=` `4.4566``        ``delta ``=` `0.0001``        ``# error message in case if test case got failed``        ``message ``=` `"first and second are not almost equal."``        ``# assert function() to check if values are almost equal``        ``self``.assertAlmostEqual(first, second, ``None``, message, delta)`` ` `    ``# positive test function to test if values are almost equal with delta``    ``def` `test_positiveWithDelta(``self``):``        ``first ``=` `4.4555``        ``second ``=` `4.4566``        ``delta ``=` `0.002``        ``# error message in case if test case got failed``        ``message ``=` `"first and second are not almost equal."``        ``# assert function() to check if values are almost equal``        ``self``.assertAlmostEqual(first, second, ``None``, message, delta)`` ` ` ` `if` `__name__ ``=``=` `'__main__'``:``    ``unittest.main()`

Output:

```FF..
======================================================================
FAIL: test_negativeWithDelta (__main__.TestStringMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/2c36bbd2c940a6c7b81a901ebfdd2ad8.py", line 34, in test_negativeWithDelta
self.assertAlmostEqual(first, second, None, message, delta)
AssertionError: 4.4555 != 4.4566 within 0.0001 delta : first and second are not almost equal.

======================================================================
FAIL: test_negativeWithPlaces (__main__.TestStringMethods)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/2c36bbd2c940a6c7b81a901ebfdd2ad8.py", line 14, in test_negativeWithPlaces
self.assertAlmostEqual(first, second, decimalPlace, message)
AssertionError: 4.4555 != 4.4566 within 3 places : first and second are not almost equal.

----------------------------------------------------------------------
Ran 4 tests in 0.001s

FAILED (failures=2)

```

Reference: https://docs.python.org/3/library/unittest.html

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