Replace element in list python by index

Replace element in list python by index. msg = raw_input("Msg: ") dmsg = list(msg) for i in range(len(dmsg)): if msg[i] == "^": dmsg[i] = " ". Here’s an example: Feb 2, 2024 · In this method, the given string is first converted into a list. However, I don't know how to modify the last element in the list. Method #1: Using string slicing. Method #1: Using Iteration C/C++ Code # Python code to replace every element # in second list with index of first element. count (optional) - the number of times you want to replace the old substring with the new string. choice to randomly select elements where you want the replacements to occur in the original list. io def f1(arr, find, replace): # fast and readable base=0 for cnt in range(arr. Modifying each element while iterating a list is fine, as long as you do not change add/remove elements to list. the same results as for lists) when the elements themselves were jagged arrays. Then, you can replace an item by assigning a new value to the specific index. Feb 5, 2024 · In Python, retrieving the indices of specific elements in a list is a common task that programmers often encounter. Jan 28, 2019 · EDIT: You can also replace the range function with an enumeration of the elements to get the index, and ignore the actual elements, like this (note I also inverted the condition, since the new slicing moved the indexes by one): Jul 13, 2018 · Variable salary is just a copy of the value from data. index() method to figure out the index of the element to replace the original list element. 4,661 3 28 42. Oct 3, 2020 · Python: Replace characters at multiple index positions in a string with the same character. Method 4: Using the next() Function With an Iterable. should take you there. copy: new = old. Method 2 – Python Replace Element in List using Python enumerate () Method 3 – For Loop. Feb 6, 2013 · In python, what is the best way to replace an element in a list with the elements from another list? For example, I have: a = [ 1, 'replace_this', 4 ] @gath: Don't aspire to write one-liners for every purpose. list_items = list(map(lambda x: new_elements[elements_to Apr 18, 2016 · Should I get the element with coordinates? How can I change the element found by my grid_index () function with 1? Similar to this question: finding and replacing elements in a list (python) but with a multi-dimensional array. Mar 1, 2023 · Method 1 – Python List Replace using Index. If you want to replace one element in listb with an element in lista, then. If there is no match, keep the original value. Bonus One-Liner Method 5: Using a Function. But, if list contains just one such item then for @arshajii's solution. if elem in mainString : # Replace the string. I know I can do it by. As to hints: Get to know the tools that Python ofters, especially list (and for Python 3 also dict) comprehensions, the ternary operator, anonymous (lambda) functions, and functions like map, zip, filter, reduce The list has been modified. insert(index + 1, i) return a it's a bit long, but i don't know if there is a better way to insert. First, you can use . Sep 13, 2013 · Replacing element in list without list comprehension, slicing or using [ ]s [duplicate] Python – Replace Character at Specific Index in String. you are iterating over the list element, but later you are using the element as an index where you need an integer instead. loc[0:15,'A'] = 16. . replace('567', '<567>') for w in words] 100 loops, best of 3: 8. Jan 3, 2017 · n is an element in your example; not an index. In this example, the index will be 3. 100 loops, best of 3: 6. The world is changing exponentially. The benefit of doing so is readability. You have to change the list element directly in order to alter the list. Can I change multiple items in a list at one time in Python? Question1: For example,my list is. That works fine. # initializing list. Similarly, replaced the element at the index 1 (which is ‘ Python') with 'Numpy'. index(item_to_replace) except ValueError: #if item is not in list return a a[index] = list_to_insert[0] for i in list_to_insert[1:]: a. The most straightforward method to replace an element in a list is by directly assigning a new value to the desired index. Summary Python List Replace. First, identify the index of the item you wish to replace. It’s a basic feature of Python lists where you simply assign a new value to the list at the specified index using the assignment operator. If it’s the second occurrence or more, then index is added in result list. from_iterable with a generator expression. – James Hirschorn Jan 14, 2022 at 16:30 Oct 23, 2022 · list = list[i for i in range(len(list)) if i in indices_to_keep] That said, sometimes you need to modify a list passed as an argument, or that may have other bindings that you can't find or update. In addition, you are creating a new list yet you return the old one. Feb 16, 2024 · Direct assignment is the simplest way to replace an element in a Python list by index. # Replace sublist with other in list. strip() for item in l] or just do the C-style for loop: for index, item in enumerate(l): l[index] = item. And for each index, replace the character at that index by slicing the string, Oct 20, 2014 · 1. If you were intending to actually change the characters of phrase, well that's not possible, as in python, strings are immutable. as you can see for such simple patterns the accepted list comprehension is the fastest, but look at the following: In [8]: %timeit replaced = [w. There are multiple ways for using if conditions in a list comprehension, but for your case you need to check the index in the (index, element) tuple and see if it returns a remainder when divided by 3. 0. Where, list_name [index_value]=new_items: This represents the specific elements of the list that you want to replace. In that case, you can use the list() function to create a copy of the list. To do that, we will iterate over all the index positions in the list. copy() new. Sep 17, 2021 · I want to identify the index of an element in the list a based on first three sub-elements of the element. To replace a character with a given character at a specified index, you can use python string slicing as shown below: string = string[:position] + character + string[position+1:] where character is the new character that has to be replaced with and position is the index at which we are Oct 10, 2023 · Python リストの要素を置換する方法はいくつかあります。Python リストの要素をインデックス化する方法、for ループ、map 関数、リスト内包の方法などがあります。この記事では、上記の Python リストの要素を見つけて置換する方法について説明します。 Mar 21, 2015 · 1. This is the most straightforward method when the index of the target element is known. list_name is the name of the list containing elements or items, followed by the square bracket [] containing the index value. Sometimes, they increase readability or performance, but often they don't. The above example yields the below output. In this, we perform the slicing of pre string, till i, and then add K, then add post values, using string slice method. Let me know if this makes sense. But if you use a pretty similar code like this. Sometimes, while working with Python data, we can have a problem in which we have two lists and we need to replace positions in one list with the actual elements from other list. B=[0,3,5,7,8] I need to replace the A list elements with zero which is not listed in B -list (index of A) What I tried is : Z=[0 if A. n = 9 # in this example. 17. l=[1,2,3,4] for i,x in enumerate(l): l[i]=x+1 this changes the list Feb 26, 2018 · I have to search all elements in a list and replace all occurrences of one element with another. In this article, we will explore some different approaches to get the index of multiple list elements in Python. : In this example, the list comprehension iterates over each element in my_list and replaces any instances of 3 with 6. 15 ms per loop. Python3. # Replace tuple according to Nth tuple element. Nov 3, 2021 · All characters in the list (except for the spaces) are “-”, so I can’t tell it to replace a specific character, I need to replace a specific position with a letter, with the value of “guess”. In the second matrix, I want to replace the second 0 with 2. See full list on datagy. seems like what you want should be as below. If you need to substitue strings you could adapt it using the i+len(substring)+1 to determine where the string ends. I want to the third and fifth item become 99. If you just want listb to be a copy of lista, then. 🤖 Jul 24, 2021 · Where B -list is the index of A[] elements that I should have. new - new substring which will replace the old substring. For e Mar 10, 2014 · In case list contains more than 1 occurrences of 'r' then you can use a list comprehension or itertools. 1. What you need is extract a list from data and access it by indexing: 5 days ago · Here, we first initialize a list lists containing six elements. Method 1: Direct Assignment. But now I#ve got a problem, that my list ist a list of lists: tilemap_1 = [ [random. For example if 'a' is detected, it would be replaced with ['vowel', 'a']. Method 3: Using the map() Function. If there is a match, replace the original value in base_list with the one from custom_list. Disruptive technologies such as AI, crypto, and automation eliminate entire industries. The element at index 1 (“banana”) was replaced with “mango”. Although lists are mutable in Python, sometimes you may need to replace an item from a list without modifying the original list (for example when working with large datasets). list_items = ['apple', 'banana', 'cherry', 1, 2, 3] # Elements to replace (can be any data type) elements_to_replace = ['apple', 1] # New elements. Method #1 : Using list comprehension This Feb 2, 2024 · In Python list, elements are replaced with other numbers in different ways. split("") but that wouldn't (I don't think) work for multiple-character elements. You can use list comprehension: l = ['a', ' list', 'of ', ' string '] l = [item. There are several methods to achieve this, each with its own advantages and use cases. Here’s an example: my_list = [1, 2, 3, 2, 4] old_value = 2. Jun 21, 2021 · similar to schwobaseggl's answer, but rather than appending to a tuple with + operator, I prefer to unpack the elements desired. # Creating a list which holds n matrices. chain. replace(elem, input_char) May 4, 2015 · It iterates through the list and checks if the current and following characters meet conditions. You may need to update specific elements or modify multiple occurrences of a value. For instance, if we have a list [1, 2, 3, 2, 4] and we want to replace all occurrences of 2 with 5, the desired output would be [1, 5, 3, 5, 4]. Not very pretty, isn’t it? If you still want to learn how one-liners work, check out my book: Python One-Liners Book: Master the Single Line First! Python programmers will improve their computer science skills with these useful one-liners. (In some cases it's slower or more complicated, or you've got some other code that has a reference to the same list and needs to see it mutated, or whatever Jun 2, 2023 · Method #2 : Using list slicing ( When sublist index is given ) This task becomes easier when we just need to replace a sublist basic on the start and ending index available and list slicing is sufficient in such cases to achieve solution to this problem. The list has been modified. Here is what I have Feb 14, 2022 · Very interesting observation, that code below does change the value in the original dataframe. This is a straightforward and explicit way to replace items. join(list) and string. Replace element of a list in python. Method 5 – Lambda Function with map () Method 6 – List Replace using List Slicing. ori = [4,1,2,1,3] # some elements inside need to be changed. list-comprehension. Direct index assignment in Python allows you to replace an element at a specific position in the list. Mar 8, 2021 · We use the list. [1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1] answered Oct 8, 2015 at 11:42. every matrix should have only one index replaced. Of course if you know the id of the char you want to replace instead of a letter you can directly set the variable i. The replace() method can take a maximum of three arguments: old - the old substring we want to replace. Using 'string. # List Initialization Input1 = ['cut', 'god', 'pass'] Dec 26, 2016 · 1. e. For example, I want to replace all the N's with 0's: Replacing items in a list is a common task while manipulating lists in Python. 00" and I was wondering what is the most pythonic (one liner would be awesome) to achieve this. But there is another problem in your code, which is the reason you got the 'Entry not found on list' output when you enter a name which would be at index 0 in the list, that is the first time you enter a blank string (enter the Enter key without input nothing), you append a Jan 10, 2017 · I have two lists containing strings. Replace List Using map () and Lambda Function. Jan 16, 2013 · It's intentional in Python that making a new list is a one-liner, while mutating a list requires an explicit loop. @pstatix you need it: slice starts at index 1, goes to the end (omitted, hence consecutive colons), in steps of 2. Feb 16, 2024 · Method 1: Assigning Directly to an Index. replace list with np. Feb 16, 2024 · By enumerating over the list, the code snippet checks if the item exists in the dictionary, and if so, replaces the item in the list directly based on its index. Jul 13, 2018 · You are unpacking from the list in for loop and creating 3 variables name, appt and salary. The function enumerate can generate the index (from 0) you need for changing the value inside the list. loc[0:15]['A'] = 16. Defining a function to replace elements can abstract the replacement logic and provide reusability and better organization, especially for more complex replacement Feb 16, 2024 · The original element is retained unless it matches the condition. With this variables it isn't possible to easily change your data structure. OR. In this, we just insert all the elements in set and then compare each element’s existence in actual list. You could use numpy. Note that the list. For example, the index of the element which contains ['4','5','6'] as its first three sub-elements is 1. g. This iterates through the elements of b, and if an element in last matches the element of b being iterated through in the loop, then it changes that value with the corresponding element of rest (first element of rest for first matching instance, etc. This goes on until the n:th matrix where I want to replace the n:th 0 with 2. random import choice. The map() function is used to apply a given function to each item of an iterable (like a list) and return a list of the Apr 18, 2022 · Stack Overflow Public questions & answers; Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Talent Build your employer brand As you can see, some of these lists contain empty elements ''. You can use enumerate to get a tuple of (index, value) from an iterable: May 17, 2023 · You can use list slices to solve your problem. I would like to replace the empty elements in the above list of list (potential size >1000) to "0. num_list = [2,1,1,1] # numbers that represent index Nov 24, 2023 · The map function can be used when you want to replace multiple elements: # List of items. I want to take each item in the base_list and search to see if there is a match for the first 3 characters in any values from the custom list. Method 3: Map Function with Lambda. The complexity is O (1), meaning it’s a constant-time operation regardless of the list size. However, is there any easier way to do this? Question2:in the situation,my target value is [99,98], my index is [2,4],so my result would be [0,0,99,0,98]. Here’s an example: Feb 16, 2024 · Method 1: Direct Assignment. If it is a vowel then that element must be replaced with a sub-list with the word 'vowel' preceding the letter. In python, negative indices gets you the element in a list/tuple counting backwards, so [-1] gets you Dec 10, 2018 · when you do for i in m: you're iterating over the elements of m, not the indices of m. In terms of performance there is no difference to other proposed methods: Jan 28, 2019 · for i in range(len(flat_data2)): mainString = flat_data2[i] def replaceMultiple(mainString, unwanted, input_char): # Iterate over the strings to be replaced. What is the best way to do this? For example, suppose my list has the following elements: data = [' Dec 3, 2019 · You may need a function that runs first to 'examine' the list of lists (e. We have few index positions in a list, and we want to replace all the characters at these index positions. replace' converts every occurrence of the given text to the text you input. Apr 24, 2023 · The list's entries can be accessed using indexing. I. This method involves iterating over the list and replacing the value directly when it matches the target value. asked Jun 15, 2017 at 19:17. l=[1,2,3,4] for x in l: x=x+1 This doesn't change the list. The two phases lead to assignment at the index at the max value cell. May 5, 2023 · Python – Replace index elements with elements in Other List. Mar 1, 2023 · I offer a true method to replace the value of a multidimensional array instead of converting it to a string first as stated in this answer. then replace the element at the index 0 (which is 'Spark ‘) with 'MongoDB. If yes, then return the element else return 0. Usually, if you don't know which one you want, you want the new list . Example code: #Create your list list_a = [1, 2, 3, 4, 5, 6, 7] #Replace the elements from index 1 to 3 i. Explanation : Element is g, converted to 7 on ith index. def swap_elements(x, t): new_x = x[:] Sep 24, 2018 · I'm going to use a simple example, but basically x is another variable and isn't linked to the list element. replace('324', '<324>'). choice (resources) for w in range (screen_width)] for h in range Feb 16, 2024 · Method 1: Using a for loop. I have considered using "". print dmsg. My code so far: def replaceZero(x): # Omitted code where I count number of 0 in x. is the answer. df. edited Jun 15, 2017 at 20:31. Apr 5, 2023 · Explanation : Element is 5, converted to 7 on ith index. If they do, it will add += and skip the next item. Find the index of max value: arr. new_value = 5. You seem to realize this for most of the way, but I think your naming scheme (i is often an index) threw you off. So pretty much you have created a list in each loop, it being the exact same. 3. This involves identifying an item with a specific value and substituting it with a new value. You can use del statements to remove indices you don't want, but each delete will change the indices of all elements following the deleted index, so Jun 15, 2017 · My best attempt is the following, but it results in a list of lists that have all values of ' ' replaced with 4, rather than the specific element. Obviously, I can iterate over the list using say i,j - but I was sure python had some Nov 10, 2013 · The following example would do this for the all elements in a list that matches what you want to replace: def replace_list_item(old, new, l): ''' Given a list with an old and new element, replace all elements that match the old element with the new element, and return the list. Feb 15, 2018 · Code: new_list2 = [["hey" if x %2 == 0 else x for x in row] for row in theList] Test Code: theList = [[1, 2, 3], [4, 5, 6], [7, 8, 9]] newList = [[1, 2, 3], [4, 5, 6 I need to iterate through the list and check whether each element is equal to a vowel ( a, e, i, o, u ). ℹ️ This article has a corresponding Replit repository that you Feb 28, 2020 · I'm trying to invert a list of lists so that the values stored at the indexes in the source list become the indexes in the new list at which the original index would now be the stored value. list[index] = lista[index] is what you want. xiº. Aug 10, 2016 · This should works: word = "test"; i = word. for every tuple t in the list lst, we apply (*t[:-1], 100). Expected output will be like: [3,2,2,1,3] My code at below totally doesn't work in the way it should. Potentially easier would be to swap around the dictionary (as suggested in some other entries) so that it's {4: 'd'} and iterate over each list inside my_list. to flatten it or at least to build up a reference of entry to location). new_elements = ['mango', 4] # Replacing in a list. As for a general function, it could be modified as such: Feb 28, 2023 · Method #1 : Using loop + set () This task can be solved using the combination of above functions. array, but np. On Python 3 this can be done via list. If the element is not present in the list, it raises a ValueError Oct 8, 2015 · Try this approach: >>> my_list = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1] >>> my_list[3:6] = [0] * 3. append did not work correctly (i. random. Of course, these ways use a recursive function to get the index of the value in the multidimensional array and to replace that with another value using the index. for elem in unwanted : # Check if string is in the main string. 2nd to 4th Sep 11, 2017 · 2. 25 ms per loop. Sep 7, 2019 · Each tuple is (index, element). Mar 28, 2024 · The syntax is given below. This results in a new list with the mapped values. We use methods like list indexing, for loop, list comprehension, and map function for this purpose. Feb 28, 2020 · I'm trying to invert a list of lists so that the values stored at the indexes in the source list become the indexes in the new list at which the original index would now be the stored value. Feb 27, 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. [1, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0] Jun 2, 2023 · Method #2 : Using list slicing ( When sublist index is given ) This task becomes easier when we just need to replace a sublist basic on the start and ending index available and list slicing is sufficient in such cases to achieve solution to this problem. Note: If count is not specified, the replace() method replaces all occurrences of the def insert_in_list(a, item_to_replace, list_to_insert): try: index = a. Python’s next() function can also be used to replace the first occurrence of an element. Direct assignment is the simplest way to replace an element in a Python list by index. It finds the first item that satisfies a condition, which could be the element to replace. ThousandFacedHero. Method #2 : Using join () + generator expression. The simplest and most straightforward way to replace elements inside a list in Python is to use this. # Initializing list. Your program as pseudo-code would replace an element if it equals the element with index of its value minus 1. insert(index, value) On Python 2 copying the list can be achieved via new = old[:] (this also works on Python 3). The following code uses a List to replace a character in a string at a certain index in Python. Aug 23, 2020 · The cleanest approach is to copy the list and then insert the object into the copy. Here’s an example: Output: ['apple', 'blueberry', 'cherry'] In the Jun 4, 2013 · You haven't initialised phrase (The list you were intending to make) into a variable yet. ). Utilizing index 0, we can change the first item on the list. If you want to replace each of elements in listb with the one with the same index in lista without creating a new list, then. There are also more advanced techniques, such as using list comprehensions and using built-in functions like enumerate. Finally, the list items are converted to a string using the join() function. Feb 16, 2024 · Be on the Right Side of Change 🚀. Than it will give back just a copy of your dataframe with changed value and doesn't change the value in the original df object. index(find, base) arr[offset]=replace base=offset+1 def f2(arr,find,replace): # accepted answer for i,e in enumerate(arr): if e==find: arr[i]=replace def f3(arr,find,replace): # in place list comprehension arr[:]=[replace if e==find else e for e Feb 16, 2024 · For instance, you have a list ['alpha', 'beta', 'gamma'] and you want to replace the element at index 1 (‘beta’) with ‘delta’, so your desired output is ['alpha', 'delta', 'gamma']. I already known the (variable) indices of list elements which contain certain string and want to split the list based on these index values. Apr 3, 2015 · 7. This operation is intuitive and very efficient because it directly accesses the list by its index and changes the value. index('t', 2); word[0:i] + "b" + word[i+1:]. list. In the example below, the new value is a value that should replace the previous value in the list, and the index is the index of the Jun 14, 2013 · The index x+1 will be out of range when x is the index of the very last element. The map function combined with a lambda function can replace list elements according to dictionary keys in a functional programming style. After that, the old character is replaced by the new character at the specified index. count(find)): offset=arr. L = [[4 if x=='' else x for x in y] for y in L] python. Method 4 – While Loop. index(4). list_name[index_value]=new_items. Lets discuss certain ways in which this task can be performed. Sep 29, 2019 · I want to replace some of my elements in a list with randomly created numbers (by index), according to my values in another list. May 3, 2023 · Method #1: Using loop + enumerate () This task can be performed using the combination of loops and enumerate function which can help to access the Nth element and then check and replace when the condition is satisfied. strip() Jun 1, 2021 · I'm currently replacing the first element of that list then placing the contents of the list into a dictionary (where the key is the old element 0 value) by doing the following: old_value = old_list[0] old_list[0] = 'new value' test_dict[old_value] = old_list If you don’t know the index of the value to be replaced, you can iterate over the values of the list and find the element to be replaced and if found, assign the new value to its index. Lastly you need your condition. index(x) not in B else x for x in A] but it returned. You are not wanting to do this, you just want to replace the text based on its position (index), not based on its contents. index(element) method returns the index of the first occurrence of the specified element in the list. For example, one of the lists [0,2,4,3,1] would become [0,4,1,3,2]. index to find an item's position in a list. Also need to split into variable number of sub-lists, i. Then zip those indexes against the values you want to use for the substitution and apply the replacements. Feb 16, 2024 · The list comprehension iterates through the original list and for each fruit, it fetches the corresponding color from the dictionary. This is what I've managed to think of so far although Feb 16, 2024 · This code uses the enumerate() function to get index and value in the loop and directly updates the list element at the given index. Jul 14, 2009 · I tried this approach, i. explanation. mainString = mainString. You simply assign a new value to the list at that index. Feb 16, 2024 · When working with Python lists, one might encounter the need to replace elements by their values. from numpy. You should modify the original list instead of the copy. – Luke. replace('1', '<1>'). To replace an element in a Python list, you can use indexing. bd iu lw hc pj qc yz ch gg qk