When checking whether a particular value is part of a sequence, you may want to use the \u201cin\u201d or \u201cnot in\u201d operators in Python.<\/p>\n\n\n\n
What are \u201cin\u201d and \u201cnot in\u201d operators in Python? In the following examples, I\u2019ll show you how to use the \u201cin\u201d operator and its negation \u201cnot in\u201d operator.<\/p>\n\n\n\n The most common example of using the \u201cin\u201d operator in Python is checking if a particular value or object is part of a list or if a specific character is part of a string. It returns a Boolean value, which depends on how the \u201cin\u201d statement was evaluated.<\/p>\n\n\n\n The \u201cin\u201d operator is used in the following format: To illustrate how the Python \u201cin\u201d operator works, look at the following examples.<\/p>\n\n\n\n As you can see, we used the Python \u201cin\u201d operator with lists, tuples and strings. Each of these sequences allows checking if the value is one of the members.<\/p>\n\n\n\n Sometimes it can be confusing if you\u2019re using the \u201cin\u201d operator with the dictionary since it contains key-value pairs. In that case, the \u201cin\u201d operator checks whether the specified value exists as a key in a dictionary.<\/strong> In our example, keys are 1<\/strong> and 2<\/strong>.<\/p>\n\n\n\n If you want to check if the value exists in a dictionary use the When paired with the \u201cnot\u201d keyword, you get the opposite result of using only the \u201cin\u201d operator. What the \u201cin\u201d operator would return as So if you wanted to check whether a specific value is not a part of the sequence, you\u2019d write it like this: Now to illustrate it, I\u2019ll use the same examples as before.<\/p>\n\n\n\n In the above examples, we again used the Python \u201cnot in\u201d operator with lists, tuples and strings. Note that the evaluation of the “not in” operator over these examples resulted in opposite Boolean values than those obtained using the “in” operator.<\/p>\n\n\n\n The same logic applies to dictionaries. If the key is not present, the \u201cnot in\u201d operator will return If you want to check if the value does not exist in the dictionary, retrieve the list of values, then use the \u201cnot in\u201d operator. It will return Although the \u201cX not in Y\u201d is logically the same as the \u201cnot X in Y\u201d statement, I recommend you to use the \u201cX not in Y\u201d always. It\u2019s more readable, and if you work with other devs on the same code it will be easier for everyone to understand the statement.<\/p>\n\n\n\n
Also known as membership operators, the \u201cin\u201d and \u201cnot in\u201d Python operators are used when you need to check whether a particular value is part of a sequence<\/strong>. That sequence can be a list, array, string, tuple, or any other iterable. If the given element is found, the \u201cin\u201d operator returns True<\/code>; otherwise, it returns False<\/code>. The \u201cnot in\u201d operator returns the opposite.<\/strong> If the given element is not found, the \u201cnot in\u201d operator returns True<\/code>; otherwise, it returns False<\/code>.<\/p>\n\n\n\nPython \u201cin\u201d operator<\/h2>\n\n\n\n
X in Y<\/code>
This statement checks whether the X value is part of the Y sequence.<\/strong><\/p>\n\n\n\nlist_numbers = [1, 2, 3, 4, 5]\nprint(1 in list_numbers) # True\nprint(10 in list_numbers) # False\n\ntuple_strings = (\"abc\", \"def\", \"ghi\")\nprint(\"abc\" in tuple1) # True\nprint(\"jkl\" in tuple1) # False\n\nstring_example = \"Learning how in and not in operators work\"\nprint(\"operators\" in string_example) # True\nprint(\"abc\" in string1) # False<\/pre>\n\n\n\n
dict_example = {\n 1: \"Value1\", \n 2: \"Value2\"\n}\nprint(1 in dict_example) # True\nprint(\"Value1\" in dict_example) # False<\/pre>\n\n\n\nvalues()<\/code> method to retrieve all values from a dictionary. Values are returned as a list, so now you can use the \u201cin\u201d operator as you would with any other list.<\/p>\n\n\n\ndict_example = {\n 1: \"Value1\", \n 2: \"Value2\"\n}\nprint(1 in dict_example.values()) # False\nprint(\"Value1\" in dict_example.values()) # True<\/pre>\n\n\n\nPython \u201cnot in\u201d operator<\/h2>\n\n\n\n
True<\/code>, the \u201cnot in\u201d Python operator will return as False<\/code>. The same applies the other way around.\u00a0<\/p>\n\n\n\nX not in Y<\/code>
This statement checks whether the X value is not part of the Y sequence.<\/strong><\/p>\n\n\n\nlist_numbers = [1, 2, 3, 4, 5]\nprint(1 not in list_numbers) # False\nprint(10 not in list_numbers) # True\n\ntuple_strings = (\"abc\", \"def\", \"ghi\")\nprint(\"abc\" not in tuple1) # False\nprint(\"jkl\" not in tuple1) # True\n\nstring_example = \"Learning how in and not in operators work\"\nprint(\"operators\" not in string_example) # False\nprint(\"abc\" not in string1) # True<\/pre>\n\n\n\n
True<\/code>. If the key is present, the \u201cnot in\u201d operator will return False<\/code>.<\/p>\n\n\n\ndict_example = {\n 1: \"Value1\", \n 2: \"Value2\"\n}\nprint(1 not in dict_example) # False\nprint(\"Value1\" not in dict_example) # True<\/pre>\n\n\n\nTrue<\/code> if the value does not exist in the dictionary, otherwise False<\/code>.<\/p>\n\n\n\ndict_example = {\n 1: \"Value1\", \n 2: \"Value2\"\n}\nprint(1 not in dict_example.values()) # True\nprint(\"Value1\" not in dict_example.values()) # False<\/pre>\n\n\n\nBest practices when using the Python \u201cnot in\u201d and \u201cin\u201d operators<\/h2>\n\n\n\n
Use the \u201cX not in Y\u201d instead of \u201cnot X in Y\u201d<\/h3>\n\n\n\n
Define
__contains__()<\/code> function for complex sequences<\/h3>\n\n\n\n