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# The best way to Subtract Arrays in Python

## The problem#

Implement a distinction perform, which subtracts one listing from one other and returns the outcome.

It ought to take away all values from listing `a`, that are current in listing `b` protecting their order.

``````arrayDiff([1,2],[1]) == [2]
``````

If a price is current in `b`, all of its occurrences should be faraway from the opposite:

``````arrayDiff([1,2,2,2,3],[2]) == [1,3]
``````

## The answer in Python#

Choice 1:

``````def array_diff(a, b):
return [x for x in a if x not in b]
``````

Choice 2:

``````def array_diff(a, b):
return filter(lambda i: i not in b, a)
``````

Choice 3:

``````def array_diff(a, b):
for i in vary(len(b)):
whereas b[i] in a:
a.take away(b[i])
return a
``````

## Check circumstances to validate our answer#

``````import  check
from answer import array_diff

@check.describe("Fastened Checks")
def fixed_tests():
@check.it('Fundamental Check Instances')
def basic_test_cases():
check.assert_equals(array_diff([1,2], [1]), [2], "a was [1,2], b was [1], anticipated [2]")
check.assert_equals(array_diff([1,2,2], [1]), [2,2], "a was [1,2,2], b was [1], anticipated [2,2]")
check.assert_equals(array_diff([1,2,2], [2]), [1], "a was [1,2,2], b was [2], anticipated [1]")
check.assert_equals(array_diff([1,2,2], []), [1,2,2], "a was [1,2,2], b was [], anticipated [1,2,2]")
check.assert_equals(array_diff([], [1,2]), [], "a was [], b was [1,2], anticipated []")
check.assert_equals(array_diff([1,2,3], [1, 2]), [3], "a was [1,2,3], b was [1, 2], anticipated [3]")
``````
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