{"id":3125,"date":"2026-11-11T06:10:03","date_gmt":"2026-11-11T06:10:03","guid":{"rendered":"https:\/\/gyanipandit.com\/programming\/?p=3125"},"modified":"2026-11-11T06:10:03","modified_gmt":"2026-11-11T06:10:03","slug":"membership-operators-in-python","status":"publish","type":"post","link":"https:\/\/gyanipandit.com\/programming\/membership-operators-in-python\/","title":{"rendered":"Membership Operators in Python (in, not in) with Examples"},"content":{"rendered":"

Membership operators check whether a value is present inside a collection such as a list, string, tuple, set, dictionary or range. Python has two of them, in<\/code> and not in<\/code>, and both return True<\/code> or False<\/code>.<\/p>\n

They make code read almost like English: if \"mango\" in fruits:<\/code> means exactly what it says.<\/p>\n

Membership Operators in Python<\/h2>\n\n\n\n\n\n\n
Operator<\/th>\nReturns True when<\/th>\nExample<\/th>\n<\/tr>\n<\/thead>\n
in<\/code><\/td>\nthe value is found in the collection<\/td>\n\"a\" in \"cat\"<\/code> gives True<\/code><\/td>\n<\/tr>\n
not in<\/code><\/td>\nthe value is not<\/strong> found in the collection<\/td>\n5 not in [1, 2, 3]<\/code> gives True<\/code><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

With Lists<\/h2>\n
fruits = [\"apple\", \"mango\", \"banana\"]\nprint(\"mango\" in fruits)\nprint(\"grapes\" in fruits)\nprint(\"grapes\" not in fruits)<\/code><\/pre>\n
Output:<\/strong><\/p>\n
True\nFalse\nTrue<\/code><\/pre>\n
With Strings<\/h2>\n
For strings, in<\/code> checks for a substring<\/strong>, so it can find whole words or parts of words. The check is case-sensitive.<\/p>\n
sentence = \"Python is easy to learn\"\nprint(\"easy\" in sentence)\nprint(\"Easy\" in sentence)\nprint(\"\" in sentence)<\/code><\/pre>\n
Output:<\/strong><\/p>\n
True\nFalse\nTrue<\/code><\/pre>\n
An empty string is considered to be inside every string, which is why the last line is True. For a case-insensitive check, convert both sides: \"Easy\".lower() in sentence.lower()<\/code>.<\/p>\n
With Tuples and Sets<\/h2>\n
vowels = (\"a\", \"e\", \"i\", \"o\", \"u\")\nprint(\"e\" in vowels)\n\nprimes = {2, 3, 5, 7, 11}\nprint(9 in primes)<\/code><\/pre>\n
Output:<\/strong><\/p>\n
True\nFalse<\/code><\/pre>\n
Sets are the fastest choice for membership checks. Python checks a set or a dictionary almost instantly, however large it is, while a list has to be scanned item by item. If you need to check membership many times in a big collection, convert the list to a set first.<\/p>\n
With Dictionaries<\/h2>\n
With a dictionary, in<\/code> checks the keys<\/strong>, not the values. Use .values()<\/code> or .items()<\/code> when you need those.<\/p>\n
marks = {\"Riya\": 91, \"Aman\": 78}\nprint(\"Riya\" in marks)\nprint(91 in marks)\nprint(91 in marks.values())\nprint((\"Aman\", 78) in marks.items())<\/code><\/pre>\n
Output:<\/strong><\/p>\n
True\nFalse\nTrue\nTrue<\/code><\/pre>\n
With range()<\/h2>\n
print(50 in range(1, 101))\nprint(100 in range(1, 100))<\/code><\/pre>\n
Output:<\/strong><\/p>\n
True\nFalse<\/code><\/pre>\n
range(1, 100)<\/code> stops before 100, so 100 is not in it.<\/p>\n
Practical Examples<\/h2>\n
1. Count the Vowels in a Word<\/h3>\n
word = \"education\"\ncount = 0\nfor ch in word:\n    if ch in \"aeiou\":\n        count += 1\nprint(count)<\/code><\/pre>\n
Output:<\/strong><\/p>\n
5<\/code><\/pre>\n
2. Validate a Menu Choice<\/h3>\n
choice = \"3\"\nif choice in (\"1\", \"2\", \"3\"):\n    print(\"Valid choice\")\nelse:\n    print(\"Invalid choice\")<\/code><\/pre>\n
Output:<\/strong><\/p>\n
Valid choice<\/code><\/pre>\n
This is much cleaner than writing choice == \"1\" or choice == \"2\" or choice == \"3\"<\/code>.<\/p>\n
3. Remove Duplicates While Keeping the Order<\/h3>\n
names = [\"Riya\", \"Aman\", \"Riya\", \"Kabir\", \"Aman\"]\nunique = []\nfor n in names:\n    if n not in unique:\n        unique.append(n)\nprint(unique)<\/code><\/pre>\n
Output:<\/strong><\/p>\n
['Riya', 'Aman', 'Kabir']<\/code><\/pre>\n
Watch Out: Nested Lists<\/h2>\n
in<\/code> only looks at the top level of a collection. It does not search inside inner lists.<\/p>\n
matrix = [[1, 2], [3, 4]]\nprint(3 in matrix)\nprint([3, 4] in matrix)\nprint(any(3 in row for row in matrix))<\/code><\/pre>\n
Output:<\/strong><\/p>\n
False\nTrue\nTrue<\/code><\/pre>\n
The items of matrix<\/code> are the two inner lists, so 3 in matrix<\/code> is False. To search inside every row, use any()<\/code> as in the last line.<\/p>\n
Practice Questions<\/h2>\n
    \n
  1. print(\"a\" in \"Banana\")<\/code><\/li>\n
  2. print(\"ana\" in \"Banana\")<\/code><\/li>\n
  3. print(2 in [[1, 2], [3]])<\/code><\/li>\n<\/ol>\n
    Answers:<\/strong> 1) True<\/code>. “Banana” contains a small “a” at index 1. 2) True<\/code>. “ana” appears as a substring. 3) False<\/code>. The list holds two inner lists, not the number 2.<\/p>\n
    Frequently Asked Questions<\/h2>\n
    What are membership operators in Python?<\/h3>\n
    in<\/code> and not in<\/code>. They test whether a value is present in a sequence or collection.<\/p>\n
    Does in check keys or values in a dictionary?<\/h3>\n
    Keys. Use value in my_dict.values()<\/code> to check values.<\/p>\n
    Is the in operator case-sensitive for strings?<\/h3>\n
    Yes. \"Easy\" in \"Python is easy\"<\/code> is False. Convert both strings to lower case for a case-insensitive check.<\/p>\n
    What is the difference between in and ==?<\/h3>\n
    ==<\/code> compares two whole values. in<\/code> checks whether one value is contained inside another.<\/p>\n
    Next: Identity operators in Python<\/a> \u00b7 Previous: Python bitwise operators<\/a> \u00b7 All operators: Python operators overview<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
    Membership operators check whether a value is present inside a collection such as a list, string, tuple, set, dictionary or range. Python has two of them, in and not in, and both return True or False. They make code read almost like English: if “mango” in fruits: means exactly what it says. Membership Operators in … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[25],"tags":[26,27],"class_list":["post-3125","post","type-post","status-publish","format-standard","hentry","category-python-tutorial","tag-python","tag-python-tutorial"],"_links":{"self":[{"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/posts\/3125","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/comments?post=3125"}],"version-history":[{"count":3,"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/posts\/3125\/revisions"}],"predecessor-version":[{"id":6130,"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/posts\/3125\/revisions\/6130"}],"wp:attachment":[{"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/media?parent=3125"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/categories?post=3125"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gyanipandit.com\/programming\/wp-json\/wp\/v2\/tags?post=3125"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}