Connect and share knowledge within a single location that is structured and easy to search. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Can a creature that "loses indestructible until end of turn" gain indestructible later that turn? You may have to convert list2 (larger list) to a defaultdict, where key is the potential value you want to check from small list, and value is either 1 (hit) or 0 (no hit, default). How do I figure out what size drill bit I need to hang some ceiling hooks? How to copy elements from one list to another in Python [Easy Way (1) You can use NumPy's setdiff1d (array1,array2,assume_unique=False). If the element doesn't exist in the list, the method will return a ValueError. Why would God condemn all and only those that don't believe in God? I tried ettanany's solution as is and it is indeed super slow for a larger list. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How do I figure out what size drill bit I need to hang some ceiling hooks? How many alchemical items can I create per day with Alchemist Dedication? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Python: Using list comprehensions to filter a list by a list of substrings, Pythonic way to check if at least one number of a list is in a tuple. FWIW my first instinct was Cardstdani set+list comprehension variant, and that's what I'd stick with unless I saw a big gain from some other suggestion. When that's the case, a better option would be converting list_1 to a set first: Not sure why the above explanations are so complicated when you have native methods available: If you want a one-liner solution (ignoring imports) that only requires O(max(n, m)) work for inputs of length n and m, not O(n * m) work, you can do so with the itertools module: This takes advantage of the functional functions taking a callback function on construction, allowing it to create the callback once and reuse it for every element without needing to store it somewhere (because filterfalse stores it internally); list comprehensions and generator expressions can do this, but it's ugly.. Checking if any elements in one list are in another. @Sharim Iqbal Ahh, maybe I screwd my implementation. I am checking using the timeit module. Conclusions from title-drafting and question-content assistance experiments How to find list items that are not in another list? When you don't have a lot of data though, making sets can be a waste of time. Python - Check if a list is contained in another list Example of finding the index of an item that has value > 100. Not the answer you're looking for? To learn more, see our tips on writing great answers. Why is reading lines from stdin much slower in C++ than Python? minimalistic ext4 filesystem without journal and other advanced features. Modified 2 years, 9 months ago. How to use the phrase "let alone" in this situation? Conclusions from title-drafting and question-content assistance experiments How do I find items in one collection that match items in another collection using LINQ? Therefore it would only exit with a "False" return value, in the case when an item from l1 is not found l2 (indeed after the very first such not-found item). If False, then the unique elements are determined first. Asking for help, clarification, or responding to other answers. I also presume you meant: It's nearly the same as the one I posted. The result of your current snippet will therefore be to exit upon the very first iteration, with either True or False depending if by chance the first items in the list happen to match. What's the DC of a Devourer's "trap essence" attack? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. In C#, how can i determine if a list has any item from another list? how to search and find multiple string from a predifined list to another list in python. Is there a way to have two lists named list1 and list2 and be able to look up the position of one entry in another. main.py Just feels like the simplest way to express "line 1: we've got the wrong data structure for this task, so create the correct one", "line 2: do what we're actually here for". If your list_one is always just the alphabet, in alphabetical order, it's probably better and simpler to get something working by using the builtin function ord. How do you manage the impact of deep immersion in RPGs on players' real-life? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Making statements based on opinion; back them up with references or personal experience. Conclusions from title-drafting and question-content assistance experiments How can I test if a list contains another list with particular items in Python? Does this definition of an epimorphism work? If you know the values are non-negative and the maximum value is much smaller than the length of the list, then using numpy's bincount might be a good alternative for using a set. Why would God condemn all and only those that don't believe in God? I realize this is a very old answer, but if one list is very long and the other is short, is there an order that would yield faster performance? For example, I want to come with the result of index i = 3 when I search for the element A[5] = 6. But I want to avoid for loops, because both lists have over 2 million elements. Unless your usecase varies widely you can go for lists, for huge inputs you can use a generator that generates the result. The computer is currently working on the. Method #2 : Using set () This problem can also be performed using the properties of difference of set and then getting the elements that are missing in a range. you can also move the try/except out of the loop, Searching values of a list in another List using Python, Improving time to first byte: Q&A with Dana Lawson of Netlify, What its like to be on the Python Steering Council (Ep. Why the ant on rubber rope paradox does not work in our universe or de Sitter universe? I'm not sure about the reason, but using bpowah's test code the curve of the function that doesn't use itertools (the one I posted) is 99% of the time under the curve of the code using dropwhile. @NoahBogart You are correct and that solution seems as good as any. Per @JonClements' comment, here is a tidier version: EXPLANATIONS: Big simplification: But now we recognize that is exactly the patter abstracted by the short-circuiting any and all built-in "short-circuiting accumulator" functions, so: which I believe is just about as simple as you can get. Hope this helps! - by using pass, which is a convenient way to instruct Python to do nothing; "pass" is typically used when "something", i.e. It wouldn't change the O complexity, but it would speed up runtime. What would naval warfare look like if Dreadnaughts never came to be? 7. try: last_found = -1 for num in L1: last_found = L2.index (num, last_found + 1) return True except ValueError: return False. Is this mold/mildew? Asking for help, clarification, or responding to other answers. Remove all the elements that occur in one list from another, Create an empty list with certain size in Python. Making statements based on opinion; back them up with references or personal experience. Is saying "dot com" a valid clue for Codenames? A dict is a better data structure for this kind of task. it's found in L2 after the position where the previous item was found), then the two lists meet the given condition and the code returns True. What information can you get with only a private IP address? Please describe how your answer improves upon what's already been presented. How can the language or tooling notify the user of infinite loops? if you really want to find the index then, first check element in array if True then only do => li.index("example"). This one is for the list containing the elements. Looking up the position of an item in a list is not a very efficient operation. Python find elements in one list that are not in the other Loaded 0% I need to compare two lists in order to create a new list of specific elements found in one list but not in the other. How to use the phrase "let alone" in this situation? @RoeeAnuar if it is just about performance, why you are not using. You're right. Ask Question Asked 2 years, 9 months ago. I was thinking along the lines of comparing the index values of list1 using < but I'm not sure. I know you don't always get to change data structure for your second list, but if you are able to from the start, then it's much faster. Find centralized, trusted content and collaborate around the technologies you use most. Although you are using a word in its plural form, for the nums variable, you need to understand that Python will use this variable to store ONE item from l1 at a time, and go through the block of code in this "for block", one time for each different item. Not the answer you're looking for? There may be a flaw in your program (with the suggested changes), that is that it would consider l1 to be a sublist of l2, even if l1 had say 2 items with value say 5 whereby l2 only had one such value. 592), Stack Overflow at WeAreDevelopers World Congress in Berlin, Temporary policy: Generative AI (e.g., ChatGPT) is banned. How to find index of element of one list in another list which includes the same elements? May I reveal my identity as an author during peer review? How do I search for an element in a list using an element in another list? Connect and share knowledge within a single location that is structured and easy to search. If you want to get an indented object with the common elements of the two sets you can use the tuple() function on the final set: Thanks for contributing an answer to Stack Overflow! I used two methods and I found one method useful over other. if there is no next element (StopIteration) it returns false (it visited the whole l2 and didn't find the current e) else it found it, so it returns true. If you know that all the values in B are unique, one way would be to create a dictionary that maps the values in B to their indices. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. The second/sets solution won't work if you have duplicates in the list (as sets only contain one of each item). Find centralized, trusted content and collaborate around the technologies you use most. How to upgrade all Python packages with pip. A shallow copy is made when the copy method is used. Find elements present in one list but not in another list (and vice versa) Ask Question Asked 2 years, 6 months ago Modified 2 years, 6 months ago Viewed 1k times 1 aList = [1, 2] bList = [2, 3] aList = [i for i in aList if i not in bList ] bList = [i for i in bList if i not in aList ] print (aList) print (bList) How did this hand from the 2008 WSOP eliminate Scott Montgomery? Syntax: list.index (element) Example: It's probably simpler to just use the built-in set intersection method, but if you have lots of lists that you're comparing, it might be faster to sort the lists. Release my children from my debts at the time of my death, Incongruencies in splitting of chapters into pesukim, Representability of Goodstein function in PA. What's the translation of a "soundalike" in French? Find items from a list which exist in another list