To find the index of the elements that meet a condition: Use a list comprehension to iterate over a range object. index() function is a handy tool for finding the index of an item in a list, it’s not the only way. of 7 runs, 100000 loops each) a = [int(random. Feb 28, 2022 · How the Python list. Using a For Loop This is because str. 1. Python List Comprehension can be used to avail the list of indices of all the occurrences of a particular element in a List. I have a list with 15 numbers. To walk over your list of words, you can use the for loop Use list. We can add a new element/list of elements to the list using the list methods such as append(), insert(), and extend(). index(x[, start[, end]]) Arguments : x : Item to be searched in the list SIDE NOTES: (a) Solution 2 (custom function setdiff_sorted) returns a list (compared to an array in solution 1). #here,i=index and j = value of that index All my codes are in Python 3. How can I find the rest o To find the index of a specific element in a given list in Python, you can call the list. The list index() method can take a maximum of three arguments: element - the element to be searched; start (optional) - start searching from this index; end (optional) - search the element up to this index I want to return a list of all the switches that are on. Fancy but not efficient, as it tests all elements of the list regardless of whether the text has been found previously or not. Related. For example, Oct 31, 2017 · For the list k1=[31. But seeing you want multiple elements, you'll need to also use regex to find all the ones that contain 'og:price:' Feb 24, 2022 · finding the index using the index() list method, using a for-loop, and finally, using list comprehension and the enumerate() function. W3Schools offers free online tutorials, references and exercises in all the major languages of the web. I had to turn down the number of test runs because the test is looking at 10000000 elements not just 100. Using enumerate() function. , we can maintain the repetition and order or remove the repeated elements in the final list and so on. # List Initialization Input1 = ['cut', 'god', 'pass'] Nov 6, 2010 · Python allows a very simple syntax to check whether something is contained in a list: censor = [ 'bugger', 'nickle' ] word = 'bugger' if word in censor: print 'CENSORED' With that approach, simply walk over your list of words and test for each words whether it’s in the censor list. Using np. I'm wondering whether there is something like string. In fact, I can quote the Zen of Python to support that: "Special cases aren't special enough to break the rules. 4+). There are various methods to extend the list in Python which includes using an inbuilt function such as append(), chain() and extend() function and using the Jul 21, 2009 · Consider x = [1] * 10000 + [2] * 1000. It may be that you need to evaluate the value of each item in the list to determine if it matches some value or pattern, and that you just want to obtain a list of the matching indices for later processing rather than the matching values. Syntax [i for i in range(len(lst)) if lst[i] == element] Here, the list comprehension checks for each element in the list and compares it with the required element. Dec 13, 2008 · If your list got large enough and you only expected to find the value in a sparse number of indices, consider that this code could execute much faster because you don't have to iterate every value in the list. list = ['a', 'b', None, 'c' ,None, 'd'] using the function index. find() will return the first element, regardless of how many there are in the html. Oct 25, 2015 · If you really do want to be able to index the items by entry number (ignoring the fact that a particular entry's number will change as insertions are made) then the appropriate structure would probably be a list of two-element tuples. Giving two numbers and a colon in between, you can specify a range that you want to get from the list I have an ancillary question though. I need to determine if all the items in this second list have the Apr 17, 2023 · There are many ways to find out the first index of element in the list as Python in its language provides index() function that returns the index of first occurrence of element in list. list. of 7 runs, 1000000 loops each) %timeit np. Table of Contents. So if you have a value 1. 0. Jul 4, 2018 · I have two lists in python list_A and list_B and I want to find the common item they share. Example. Learn more Explore Teams Oct 18, 2018 · I have a list of strings, some of them are None. If you want efficiency, you can use dict of dicts. mylist[0] succeeds when you have at least one element, but doesn't complain if you actually had 30 elements. max(your_tensor). May 2, 2012 · I want to find a way to get all the sub-elements of an element tree like the way ElementTree. Increment the loop counter i by 1 in each iteration. 5) for i in range(1000)] %timeit Examples 1. The syntax is list[start:end:step]. Finding the first element in a 2-D list can be rephrased as find the first column in the 2d list. See How do Python's any and all functions work? for an explanation of all and its counterpart, any. Try: def find(s, ch): return [i for i, ltr in enumerate(s) if ltr == ch] This will return a list of all indexes you need. I made a function to do this which is below: def Skip to main content Here's the Pythonic way to do it: data = [['a','b'], ['a','c'], ['b','d']] search = 'c' any(e[1] == search for e in data) Or well, I'm not going to claim this is the "one true Pythonic way" to do it because at some point it becomes a little subjective what is Pythonic and what isn't, or which method is more Pythonic than another. Elements can be added to the List by using the built-in append() function. The benefit of this method is that if you want the "second" element in a 2d list, all you have to do now is a_transposed[1]. P. By combining them, you get what you are looking for, in this case the index value 3. Below are two examples where list. To find index of element in list in python, we are going to use a method list. Find the index of an element in a list using for loop. That’s why lists are heterogeneous collections: Dec 27, 2016 · Here is a pythonic and optimized approach using itertools. Oct 4, 2019 · The count is necessary, if the algorithm is to be expressed this way, for an index variable (i) to iterate through all possible index values. item()-your_tensor))<0. Jul 31, 2011 · @KellyBundy yes, pyx means Cython. All solutions are fastest at location 100%, with the two reversed solutions taking pretty much no time for that, the double-reverse solution taking a little time, and the reverse-copy taking a lot of time. – Jan 22, 2022 · A common problem in Python is finding out where a specific item is in a list. In this example the below code defines a function, `multiplyList`, to find the product of list elements using a traversal approach. takewhile():. find_all() will return a list. index() – Single Occurrence of element in the list. Python Mar 18, 2023 · Usually, we require to find the index, in which the particular value is located. nonzero()) Here I want to get the index of max_value in the float tensor, you can also put your value like this to get the index of any elements in tensor. . index('s') I will get Dec 5, 2012 · List comprehension is a shortcut to loop an element over list which after "in", and evaluate the element with expression, then return the result to a list, also you can add condition on which result you want to return >>> [expression(element) for **element** in **list** if condition ] This code does nothing but return all pairs that zipped up. Aug 18, 2023 · In this article, we will be going to understand how to get all the indices of an element in a list in Python and we will also cover a few of the best approaches to do so. For e. Python lists, like all Python data types, are objects. There is a workaround but it's quite a bit of work: Write a sort algorithm which sorts the array and (at the same time) updates a second array which tells you where this entry was before the array was sorted. Do you need more explanations on how to find the index of an element in a nested list in Python? Then you should have a look at the following YouTube video of the Statistics Globe YouTube channel. I do it by indexing it in a dictionary. Feb 19, 2020 · . The following screenshot depicts the list and how index() method finds a match for the element and returns its index. Ways to fin In Python, how do you get the position of an item in a list (using list. Provide details and share your research! But avoid …. I only got the position of the positive values in the code. find_all() which can return all found indexes (not only the first from the beginning or the first from the end). This method simplifies the process of searching for an element, eliminating the need for manual loops or conditional statements. I don't want to use it anymore, though I can still use it currently. Oct 16, 2015 · @ekhumoro: I'm actually partial to the sequence unpacking method, because it verifies the assumption that the sequence only has one element. i want to get a new list of all the Indexes of None. The index() method will return the first index of the value you specify. Jul 2, 2024 · Multiply all numbers in the list using traversal by index. For example, if my_list is a list and my_element is an element in the list, you can find all the indices of my_element with [i for i in range(len(my_list)) if my_list[i] == my_element]. You are using . index(None) will only return the first appearance, n= 2, while i want to see n= [2,4]. In this case the sum is 18. Jun 13, 2017 · Now available on Stack Overflow for Teams! AI features where you work: search, IDE, and chat. To find the index of an element in a list using for loop, we will simply iterate through the list and check for each element. This is the easiest and straightforward way to get the index. However, because Python lists can contain duplicate items, it can be helpful to find all of the… Read More »Python: Find List Index of All Occurrences of an Element May 29, 2015 · Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. Unfortunately, the question was not well-posed so there are answers to different questions, here I try to point the answer to the same question. Find List Index of All Occurrences of an Now available on Stack Overflow for Teams! AI features where you work: search, IDE, and chat. Oct 10, 2013 · Is there a simple way to index all elements of a list (or array, or whatever) except for a particular index? E. Use list slicing to split the even/odd index elements into two lists, e. While Python’s list. How to find the indices of items matching a condition. 5) for i in range(10)] %timeit [i for i, e in enumerate(a) if e != 0] 683 ns ± 14 ns per loop (mean ± std. thanks you. Specifically, here is what we will cover in depth: An overview of lists in Python. Example #1: Index of specific values. Apr 30, 2023 · Python: Get index of item in List. How to use alternative methods like list comprehensions to find the index of an item in a list. To find the index of an item in a Python list, you can also use the built-in . Fro example I get back [[1,1],[1,2],[1,3],[3,8],[4,8],[5,8]] and would like [[1,1:4],[3:6,8]] primarily because my data does come in nice windows and the list of indices is huge. The list would look something like this: list = [[x,y,x], [x,y,y], [y,y,y]] Feb 12, 2024 · Union of a list means, we must take all the elements from list A and list B (there can be more than two lists) and put them inside a single new list. Jul 1, 2019 · l=[1,2,2,3,4,5,5,5] # Your list indexes=[] # Your output list for elem in set(l): indexes. If there are duplicate elements inside the list, the first index of the element is returned. Get the n-largest/smallest elements from a list in Python In Python, you wouldn't use indexes for this at all, but just deal with the values—[value for value in a if value > 2]. Share. How to find the indices of all items in a list. index () returns the index of first occurrence of an item in list. – Jun 19, 2024 · Adding Elements to a Python List Method 1: Using append() method. Mar 18, 2022 · In this tutorial, you’ll learn how to use Python to find the list index of all occurrences of an element. – To find the index of an element in a list, you use the index() function. Jun 4, 2022 · We also discussed finding all the indices of the minimum element in the list in case of multiple occurrences of the minimum element. but you didn't explain your answer well. (b) If you aren't sure if the elements are unique, just use the default setting of NumPy's setdiff1d in both solutions A and B. @eric on the contrary: it would be really bizarre if L[idx] did do this in base Python. Apr 30, 2023 · Find all indices of an item in List using list. Stack Overflow is a community of programmers who can help you solve your problems. Nov 19, 2009 · This is already stated by the top-voted answer. rfind() to get the index of a substring in a string. Mar 13, 2018 · If your objects are not hashable, but still orderable, you might wanna consider using sorted to match both lists. this is what I want: newk1=[0, 0, 0, 681. Then you need to extract all repeated values. It sequentially multiplies each element in the list. index(letter) But this code gives only the first index. 1) How to Find the Index of a List Element Using The index() Function. n = list. Nov 13, 2023 · In Python, the index() method is a powerful tool that allows you to find the position or index of a specific element in a list or string. Output: 0,3. index('*berry') Apr 10, 2024 · # Find the index of elements that meet a condition in Python. This approach gives the leftmost index of the minimum element in case of multiple The best method to solve this problem is to enumerate the list, which will give you a tuple that contains the index and the item. Input: my_list = [1, 2, 3, 1, 5, 4] item = 1. How will you find the index of a list element? Example: In the following, the list consists of names of books as its elements. Covering popular subjects like HTML, CSS, JavaScript, Python, SQL, Java, and many, many more. index(elem)) In the for loop, each element of the set is taken and the index of the element in the list is taken out using list. Method #1: Using Iteration C/C++ Code # Python code to replace every element # in second list with index of first element. Jul 19, 2013 · If your list is called a, you can make a list comprehension to get the row indices where first column is equal to value: rows = [i for i in range(0,len(a)) if a[i][0]==value] However, I'm sure there are whole libraries that parse arrays or lists in X dimensions to retreive all kinds of statistical data out there. Using enumerate, that would be done as follows. index) using fuzzy matching? For example, how do I get the indexes of all fruit of the form *berry in the following list? fruit_list = ['raspberry', 'apple', 'strawberry'] # Is it possible to do something like the following? berry_fruit_at_positions = fruit_list. Please notice that number of elements is not defined. To find multiple elements of an element in the list, you can use the index() method multiple times by setting the start index to the previously found index. You can find the index of the maximum or minimum value in a list by passing the result of max() or min() to the index() method. 0, 581. find() and string. Yes, as some of you indicated, what I need is the index range. find(s) function returns -1 when no match is found, so I'd call that Pythonic. The following lists are all valid: my_list = [1, "Erik", { 'age': 39 }] # This is a list with three lists inside game_board = [[], [], []] Using the list() function. index = mylist. The index of first item is 0, the index of second item is 1, and so on. Lists can contain objects of different types. There are various orders in which we can combine the lists. Index of List Elements. How to find a single item’s index in a list. Here "on" will equal True and "off" equal False. Example Jun 22, 2021 · Note: In Python, list elements start at index 0 (the first item is indexed 0) and we can keep adding more items. On the question, here's one possible way to find it (though, if you want to stick to this data structure, it's actually more efficient to use a generator as Brent Newey has written in the comments; see also tokland's answer): Sep 11, 2023 · To find the index of a list element in Python, use the built-in index() method. Suppose you want to find all indices where a specific value appears in a list (e. Each element in a list is associated with a number, known as an index. n==30 If you simply want to determine if the list contains any element that matches and do it (relatively) efficiently, you can do Feb 6, 2009 · The x-axis is for the location of the searched element: 0% means it's at the start of the list, 100% means it's at the end of the list. append(i) print index Mar 14, 2012 · If you can't sort the array, then there is no quick way to find the closest item - you have to iterate over all entries. Simple. After you find each match, reset this parameter to the location just after the match that was found. I've run the tests a lot of times, so I'm pretty sure about the results. list index() parameters. In Python 3: for (i, item) in enumerate(hey, start=1): print(i, item) Or in Python 2: for (i, item) in enumerate(hey, start=1): print i, item Apr 9, 2021 · Adding elements to the list. highest value). We look at the code to achieve this with its pros and cons. Append item at the end of the list. The a_transposed object is already computed, so you do not need to recalculate. Jun 9, 2011 · This solution uses np. e. 43 µs ± 102 ns per loop (mean ± std. My code looks like following: index = [] for i, x in enumerate(lst): if x > 0: index. There are many methods to achieve that, using index(), etc. How indexing works. If it matches we can print the indices. Python List index() Python’s list data type provides this method to find the first index of a given element in list or a sub list i. I'll deal with the elements in every index range later. Method 3: Get index of element in Python List using enumerate() function. In many cases, Python makes it simple to find the first index of an element in a list. no Method Description; 1: append() Used for adding elements to the end of the List. The append() method will accept only one parameter and add it at the end of the list. You have to find the index of the element/book – “Rich Dad Poor Dad“. In this example, we will take a list of strings myList, and find the index of 'mango' in this list. Assuming all elements in both lists have a match. Jun 18, 2024 · Other Methods: Get Python List Index. Dec 21, 2023 · Usually, we require to find the index, in which the particular value is located. 2: copy() It returns a shallow copy of a list: 3: clear() This method is used for removing all items from the list. Check if a condition is met and return the corresponding index if it is. Before we delve into how you could find the index of an element in a list, we do a small recap on what lists are, in Python. Accessing the single elements by index is very slow because every index access is a method call in python numpy. Learn how to find an element in a list using Python with different methods and examples. We use these index numbers to access list items. Only one element at a time can be added to the list by using the append() method, for the addition of multiple elements with the append() method, loops are used. 0 at index 2, and at index 9, then . I know when having a list there is the Syntax: k=[1,2,3,4,5,6,7] k2=[i for i in k if i>5] k2=[6,7] Is there a similar way when having a lists of lists as an Input? Is it additionally possible to get the indices of the elements larger than that Nov 11, 2009 · Besides len you can also use operator. index(value,start,end) Parsing the above method: value is the target value that you are searching for. The list is the widely used Python data structure and it can be extended by adding elements to the list. Let’s delve into some alternative methods, such as using a for loop or list comprehension, and understand their usage and effectiveness. index('mpilgrim') What is the equivalent for a 2 or n dimensional list? Aug 18, 2023 · In this article, we are going to learn different methods of extending a list in Python. index() which will only find the first occurrence of your value in the list. unique to find the indices of all unique elements in a list. Let’s see the example to add the element ‘Emma’ at the end of the list. For a normal list both are equivalent, but length_hint makes it possible to get the length of a list-iterator, which could be useful in certain circumstances: Aug 12, 2024 · Python List index() The list index() method helps you to find the first lowest index of the given element. In this article, we'll go through how you can find the index of a particular element which is stored in a list in Python. Topics Python Note in Python 2. Here is the general syntax: list. where on an array (including the time to convert the list to an array) is slightly slower than a list-comprehension on a list, for finding all indices of all unique elements. Jul 18, 2023 · Include the index i in the new list if the element at that index matches the desired element. 4421. Finding the index of elements based on a condition using python list comprehension. count() is a O(N) job (all elements in the list are compared to count) and you are doing this in a loop over N elements, giving you quadratic performance, O(N^2). Nov 30, 2017 · This will return the tuple for the first element found or None if no element is found (you can also remove the None argument above in it will raise a StopIteration exception if no element is found). Is there any way to return every index of same values in the list. from itertools import takewhile from operator import not_ len(lst) - sum(1 for _ in takewhile(not_, reversed(lst))) - 1 Jan 28, 2015 · How to find all occurrences of an element in a list (20 answers) Python - get index of list from which on all further entries satisfy condition. Existing answers here use the built-in function all to do the iteration. pop(0). And the first answer to the question is really extensive in all Python ways to do this. EDIT FOR REOPENING: the question has been considered dupplicate, but I'm not entirely convinced: here this question is roughly "what is the most Pythonic way to find an element in a list". S. So, to find other occurrences of item in list, we will call list. index() is more efficient. For understanding what is the best answer we can do some timing using the different solution. Jul 7, 2015 · You want to pass in the optional second parameter to index, the location where you want index to start looking. print((torch. Jul 18, 2012 · Built-in function max(a) will find the maximum value in your list a, and list function index(v) will find the index of value v in your list. To know where in a Python list a specific item is you can use the list index() method that returns the index of the item if the item is in the list. Edit: As @RikPoggi correctly points out, if the number of matches is high, this will introduce some overhead because colour is iterated twice to You can get a list of all matching elements with a list comprehension: [x for x in myList if x. For example, in the following case, we want to find all indices that 2 appears in. We transform a and m into a list of pairs (element from a, element from m), and iterate over the pairs. Method 1: List Comprehension. This index variable is needed to mutate each element in the list. index() method on the list object and pass the specific element as argument. n == 30] # list of all elements with . Use enumerate() to add indices to your loop instead: This answer is 33 times faster than @Escualo assuming that the list is very large, and assuming that it's already an np. The "bug" you've described is an interesting case. Is there any way I can retrieve all at once those items in aList having as indices the values in myIndices? Example: > Jul 27, 2023 · Practical example: Find the index of the maximum/minimum value. singleitem, = mylist verifies that you've got exactly one element, no more, no less. When answering questions with existing answers, be sure to review those answers, and only add a new answer if you have a different solution, or a substantially improved explanation. The loop body executes 1000 times and . – Oct 12, 2017 · Well, I didn't downvote you. Positions are numbered from zero to the length of the list minus one. So for a 10-element list 100 steps are executed, for a 1000 element list 1 million, etc. So now I just want to return a list of all the True values and their position. For example, I have a list containing some same values like: mylist = [(A,8), (A,3), (A,3), (A,3)] I want to return: index_of_A_3 = [1, 2, 3] Dec 26, 2021 · First you need to figure out which elements are repeated and where. Learn more Explore Teams Jun 29, 2022 · Find Index of a List Item Using the index() Method. To get the index of an element in a Python list using the enumerate() function, we can iterate over the list and compare each element with the target value. According to Python docs, index must "Return zero-based index in the Mar 18, 2022 · One of the most basic ways to get the index positions of all occurrences of an element in a Python list is by using a for loop and the Python enumerate function. That smells like O(n*n) to me but is no proof. split(' ') my list is ['5', '4', '9'] and I need to sum all elements in this list. You need to iterate through that list. The element at index 0 is the first element in the list, the element at index 1 is the second, and so on. c). This is a one-liner using enumerate(). Or your other option as suggested is to use . The enumerate function is used to iterate over an object and returns both the index and element. even = my Jan 3, 2011 · NumPy has the efficient function/method nonzero() to identify the indices of non-zero elements in an ndarray object. Syntax: May 3, 2023 · In this article, we will be going to understand how to get all the indices of an element in a list in Python and we will also cover a few of the best approaches to do so. index(ch) will return the index where ch occurs the first time. The following example defines a list of cities and uses the index() method to get the index of the element whose value is 'Mumbai' : Aug 28, 2023 · Inside the loop, add the value at the current index of the list to the sum using the add() method of the operator module. Given it returns a list of indices, is there any way in numpy to coalesce those indices into a minimal list of slices. Could you please help me. To get the index of all occurrences of an element in a list, you can use the built-in function enumerate(). For example, let’s find the first string that equals “Bob” in a list of strings: To find the index of a character in a string, use the index() method on the string. Nov 29, 2009 · You can use enumerate to pair up list elements and their index: >>> l = [('ba',4), ('hh',5), ('gg', 25)] >>> [i for i, e in enumerate(l) if e[0] == 'hh'] [1] For sorting you can use a lambda expression as shown by others, or you can pass an operator. index () As list. May 24, 2019 · I am trying to find the indices of the starting position of each positive value sequence. getchildren() does, since getchildren() is deprecated since Python version 2. Jul 21, 2020 · How to get the index of an item in a Python List? Having understood the working of Python List, let us now begin with the different methods to get the index of an item of the List. Jan 20, 2016 · In Python I have a list of elements aList and a list of indices myIndices. It was introduced to solve the loop counter problem and can be used as follows: Jan 16, 2023 · We can get the index of an element in Python List using an index() funtion. . Description. index() method works. index(elem, start)!That uses a for loop in C (see its implementation list_index_impl function in the source of CPython's listobject. The YouTube video will be added soon. length_hint (requires Python 3. and I want to get a list of all elements from the list of lists larger than a certain threshold. Obviously if you start with an ndarray it will be much faster: Mar 8, 2014 · Given: x = ['w', 'e', 's', 's', 's', 'z','z', 's'] Each occurrence of s appears at the following indices: 1st: 2 2nd: 3 3rd: 4 4th: 7 If I do x. index(1. Python List Index Multiple. Explanation: The output contains all the index of element 1 in the my_list. Jun 26, 2011 · def index(L,v) ''' Return index of value v in L ''' pass I need help with implementing this function using recursion. This is all I have but it only return the position of the first occurrence of True (this is just a portion of my code): Python has string. But sometimes require to find all the indices of a particular value in case it has multiple occurrences in the list. You can even create a list of lists. index(element) The list. abs((torch. " Feb 14, 2013 · For those wondering, you can just as easily store the matching indices as the result of the list comprehension if your use-case requires it. So, if the number of test strings you're trying to find in the list also increases, you might want to think about using a dictionary to create a lookup table once, then subsequent searches for test strings are cheaper. index(x) will only return the index in the list of the first item whose value is x. To find the index of an element in a list using the index() function in Python, you can directly call the index() method on the list with the element you are searching for as the argument. index(float("nan")). diff is slow because it has to first convert the list to a ndarray . Mar 9, 2009 · It instead makes two copies of lists (one from the start until the index but without it (a[:index]) and one after the index till the last element (a[index+1:])) and creates a new list object by adding both. As a practical example, find the index of the maximum or minimum value in a list. – Sep 11, 2013 · Assuming you are talking about a list, you specify the step in the slice (and start index). remove() has to skip 10000 elements every time it's invoked. 0 occurs in the list. index(). My code to do so is the following: both = [] for i in list_A: for j in list_B: if i == j: both. 0) will always return 2, no matter how many times 1. Return the new list. What is the most efficient way to obtain the indices of the elements that do hav For a one dimensional list, the index of an item is found as follows: a_list = ['a', 'b', 'new', 'mpilgrim', 'new'] a_list. Usually dealing with indexes means you're not doing something the best way. 5, 105, 72, 31] As a beginner in Python I could not figure it out. Hugh's answer shows a generator function (it makes a difference if the list of indexes can get large). To find the index of the minimum element in a list in python, I would suggest you use the min() function with the index() method. Really new to recursion stuff so any advice would help! Mar 10, 2022 · In this short tutorial, learn to find the index of an element in a list in Python. Also, Python's 'something'. My input: 3 5 4 9 After input I delete first element via l. Ways to fin Jun 29, 2013 · I'm trying to get a list of the indices for all the elements in an array so for an array of 1000 x 1000 I end up with [(0,0), (0,1),,(999,999)]. You probably know the normal list access to get an item, e. r. Sep 23, 2021 · In the next section, you’ll learn how to use a list comprehension in Python to find all indices of a substring in a string. Oct 5, 2011 · Suppose I have to find each index of letter 'e' in the word "internet": letter = 'e' word = 'internet' idx = word. There are a few ways to do that. , mylist[3] will return the item in position 3 milist[~3] will return the whole l Dec 18, 2017 · For floating point tensors, I use this to get the index of the element in the tensor. Avoid looping through all the elements in Python, it is slower than in C. 7, map returns a list, so there is no need to pass to list. Sep 26, 2020 · I'm trying to get the index of all repeated elements in a numpy array, but the solution I found for the moment is REALLY inefficient for a large (>20000 elements) input array (it takes more or l Oct 27, 2018 · I'm trying to find the indexes of all the elements in a python list of lists. 5, 0, 0, 0], I would like to add a constant for example 100 to the first non-zero element in the reverse list. random()>0. itemgetter as the key argument to sorted : Jun 9, 2015 · Using a comprehension list, loop over the list and check if the string has the Hello! string inside, if yes, append the position to the matches list. I have two lists: a = [2,3,5,2,5,6,7,2] b = [2,5,6] I would like to find when all the indexes of the second list (b) are in the first list (a), so that I get something like this: indexes of b in a: 3, 4, 5 or b = a[3:6] Nov 26, 2015 · A little bit of "amateur" approach and yet very easy to understand: Creating a flag boolean value that will execute the result based on if it is True or False with a nested for loop. t length of the list. Aug 23, 2021 · We will use for loop to iterate the list to find all the occurrences of any element in the list. But if one desires to get the last occurrence of element in list, usually a longer method has to be applied. Print the sum of the list elements using the print() function and a message. Use the index() method to find the index of an item 1. g. index() method. index() method (which returns the index of the first element of the required type) and the value is inserted into the Aug 4, 2016 · It won't be efficient, as you need to walk the list checking every item in it (O(n)). 0, 72, 105. index () repeatedly with range arguments. at first glance, I would argue that you said not to use the default data structure list, dict as a variable but then you used 'a list' to create a variable which if not properly worded might be confused by someone who doesn't know what they are doing and think you have contradicted yourself This method will iterate over every element of your list, so the runtime cost increases as the list becomes bigger. After . How to Use a Python List Comprehension to Find All Indices of a Substring in a String. find(). The new list will only contain the indexes of the elements that meet the condition. If the condition you want to check is "is found in another container", see How to check if all of the following items are in a list? and its counterpart, How to check if one If you have a list in python, and want to extract elements at indices 1, 2 and 5 into a new list, how would you do this? This is how I did it, but I'm not very satisfied: >>> a [10, 11, Mar 26, 2020 · But removing an element from a list can change the indices of all elements in the list so the predefined indices do not point to the correct elements anymore. That is my code: Mar 30, 2020 · Summary of the answers. array(). Demonstrations with lists `[1, 2, 3]` and `[3, 2, 4]` yield outputs of 6 and 24, respectively. Examples: Maintained repetit Oct 21, 2010 · A Pythonic way to find the index of the maximum list element would be . Let's discuss certain ways to find indices of value in the given list of Python. May 2, 2022 · When you're learning to code, you eventually learn about lists and the different operations you can perform on them. where and np. dev. Find List Index of All Occurrences of an Feb 28, 2023 · In this article, we will be going to understand how to get all the indices of an element in a list in Python and we will also cover a few of the best approaches to do so. append(l. , any number of elements, in the original order)? I thought of looping through the decimal integers 1– Jun 23, 2015 · But what if I want to get another index ranges that need the value > 20 for the next time? Ugly wrote another function? Is there a simple way to get the index range in a general level? Update. Let’s take a look at how you can find all indices of a substring in a string in Python without using the regular expression library. Mar 29, 2024 · Given two lists of strings, where first list contains all elements of second list, the task is to replace every element in second list with index of elements in first list. a = [int(random. Time comparison of the two answers w. nonzero(a)[0] 4. Try [float("nan")]. Jul 30, 2024 · We will cover different examples to find the index of element in list using Python, and explore different scenarios while using list index() method, such as: Find the index of the element; Working on the index() With Start and End Parameters; Working of the index() With two Parameters only; Index of the Element not Present in the List Jun 22, 2020 · Due to list. 0001). Note: The enumerate build in brings you the index for each element in the list. In the video, we explain in some more detail how to find the index of an element in a nested list in Python. You can sort the lists indexes and pair the results May 5, 2012 · I am quite new and I hope it's not too obvious, but I just can't seem to find a short and precise answer to the following problem. Problem Formulation: Given a list. Example Input: my_list = [1, 2, 3, 1, 5, 4] item = 1Output: 0,3Explanation: The output contains all the index of element 1 in the my_list. For example, let’s find the first occurrence of […] Jun 24, 2024 · The elements in a list can have any data type, and they can be mixed. Apr 18, 2024 · S. append(i) Oct 9, 2023 · This post will discuss how to find the index of all occurrences of an item in a Python List. Which is easy to do - just use the built-in library function zip, as follows: for a_element, m_element in zip(a, m): s[a_element] = m_element Apr 9, 2024 · Get only the even or odd index elements of a Python List; Get only the even or odd index elements of a Python List using a for loop; Get only the even or odd index elements of a List using islice() # Get only the even or odd index elements of a Python List. index() method returns an integer that represents the index of first occurrence of specified element in the List. l[2] to get the third item. 7. Asking for help, clarification, or responding to other answers. How can I produce all 32,768 combinations of those numbers (i. I have a list that has a minimum element that is present multiple times like a = [1,2,1,1,4,5,6] And I want Python to return the element 1 and all the indices in the list where 1 is present. Sep 24, 2010 · In some of my code I put a series of objects in a list and I build an additional list out of their attributes, which is a string. xlaj eommsnc wfuarm tgydsa kmfka gdqa fhes knev ndmyrqd mttmf