Spying on a smartphone remotely by the authorities: feasibility and operation, How to play the "Ped" symbol when there's no corresponding release symbol, Cultural identity in an Muti-cultural empire. Asking for help, clarification, or responding to other answers. Given two lists, one of key and other values, convert it to dictionary with list values, if keys map to different values on basis of index, add in its value list. If all you need is a single plain for loop then that last step is unnecessary (and indeed unhelpful if e.g. Do I remove the screw keeper on a self-grounding outlet? Method #2 : Using map() + list() + zip() + tuple() The combination of above functions can be used to solve this problem. acknowledge that you have read and understood our. However, you may also want to consider if the argument has a __iter__ method or __getitem__ method. How to play the "Ped" symbol when there's no corresponding release symbol. how to flatten a 2D list to 1D without using numpy? tuple([el for el in l if (el==5 or el==6)]). As of version 2.4, you can flatten more complicated, nested iterables with more_itertools.collapse (source, contributed by abarnet). str (anything) will convert any python object into its string representation. What does that mean? Connect and share knowledge within a single location that is structured and easy to search. @juanpa.arrivillaga it's a simple and natural extension of the question, though. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing. You will be notified via email once the article is available for improvement. Here's an example: . Are there ethnically non-Chinese members of the CCP right now? Is there any potential negative effect of adding something to the PATH variable that is not yet installed on the system? How to add values to a dictionary from a list with same key values in Python? As evidence, you can use the timeit module in the standard library: Explanation: the shortcuts based on + (including the implied use in sum) are, of necessity, O(L**2) when there are L sublists -- as the intermediate result list keeps getting longer, at each step a new intermediate result list object gets allocated, and all the items in the previous intermediate result must be copied over (as well as a few new ones added at the end). Python zip magic for classes instead of tuples, My manager warned me about absences on short notice, Identifying large-ish wires in junction box. d contains now {1: ('A', 'B'), 2: ('C',)}. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, Why on earth are people paying for digital real estate? In python, there are several canonical . (Ep. Are there ethnically non-Chinese members of the CCP right now? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Use the tuple() method to convert the list res into a tuple res_tuple. Morse theory on outer space via the lengths of finitely many conjugacy classes. some sequence type against known cases, like. 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6), append multiple values for one key in a dictionary, Convert list of tuples of several values into dictionary in Python 3.8, Add multiple value to a key in Python dictionary. Python zip magic for classes instead of tuples, Is there a deep meaning to the fact that the particle, in a literary context, can be used in place of , Brute force open problems in graph theory. Perhaps below code could solve the issue with satisfying quality (for the python3): Thanks for contributing an answer to Stack Overflow! If you need to drop nan values, you can do that after flattening as well: Also, future versions of Pandas seem to prefer to_numpy over values. flatten list of lists of lists to a list of lists. It acknowledges that there are many ways to do something but that some are more in the spirit of the language. Convert list of integers to an integer python. It supports any level of nesting, works iteratively and without libraries: I see lots of solutions to this that rely on an import. Can Visa, Mastercard credit/debit cards be used to receive online payments? Create a dictionary called res with the key key and the value test_list. Convert list or numpy array of single element to float in python Not the answer you're looking for? The reason your function didn't work is because the extend extends an array in-place and doesn't return it. What is the Modified Apollo option for a potential LEO transport? 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Why do keywords have to be reserved words? it fails when all elements are not list. critical chance, does it have any reason to exist? is faster than the shortcuts posted so far. critical chance, does it have any reason to exist? The auxiliary space complexity of this code is also O(n), since the filter function creates a new list that contains all the elements in the original list except for the element at index K. Time complexity: O(n) where n is the length of test_list.Auxiliary space: O(n) where n is the length of test_list since we are creating sets to store the keys and values. What is the Modified Apollo option for a potential LEO transport? One way is to use reduce with lambda x: x. #list my_list = ['Python', 'Django', 'Javascript', 'Nodejs'] my_string = "" for i in my_list: my_string += i print(my_string) let's explain. You're slicing the list, which return lists. Connect and share knowledge within a single location that is structured and easy to search. This method creates a lambda function to check if each element in the list is not equal to the element at index K, and uses the filter() function to return a list with only the elements that pass the lambda function condition. How to iterate for specific elements in a list? To learn more, see our tips on writing great answers. To me the list comprehension one doesn't. Whenever flist is returned, it is extended to the parent's flist in the list comprehension. Time complexity: O(n), where n is the length of the input list test_list. This can flatten both simple and complicated containers (see also Demo). Would a room-sized coil used for inductive coupling and wireless energy transfer be feasible? What is the proper way to iterate through a list with one item in python? (The default initial value is 0, which is not a list.). Is a dropper post a good solution for sharing a bike between two riders? This may save from reinventing the wheel. Can you work in physics research with a data science degree? @ekhumoro: I'm actually partial to the sequence unpacking method, because it verifies the assumption that the sequence only has one element. This is one of the ways in which this task can be performed. But I saw this code recently here: This answer only works for rectangular array (matrix) structures and not when the lengths of contained lists are not equal. To learn more, see our tips on writing great answers. Approach #1 : Naive Method Simply iterate each element in the list and print them without space in between. Find centralized, trusted content and collaborate around the technologies you use most. I tested most suggested solutions with perfplot (a pet project of mine, essentially a wrapper around timeit), and found, to be the fastest solution, both when many small lists and few long lists are concatenated. Connect and share knowledge within a single location that is structured and easy to search. Conversion of data types is the most common problem across CS domain nowdays. I've been asked to accept a list of integers (x), add the first value and the last value in the list, and then return an integer with the sum. When are complicated trig functions used? We want to convert this list of lists in to a single flat list, that should contain only integers like, Copy to clipboard [1, 2, 3, 4, 5, 11, 22, 33, 44, 55, 17, 18, 19, 20, 21] There are different ways to do this, Frequently Asked: Print all items in a List with a delimiter in Python Python : How to remove multiple elements from list ? 15amp 120v adaptor plug for old 6-20 250v receptacle? ), works with any combination and deepness of nesting, works also if top level contains bare items, fast and efficient (you can flatten the nested iterable partially, without wasting time on the remaining part you don't need), versatile (you can use it to build an iterable of your choice or in a loop). 1 Can't you use slicing: float (list_ [0]) = 4.0 - Kyrubas Making statements based on opinion; back them up with references or personal experience. Create a list comprehension that creates a list of lists where each inner list contains a single integer from the original list. My comment on Peter's answer was first. This approach first creates a new list new_list that contains all elements of the input list except the one at index K. Then, it creates a dictionary with the key at index K and the new_list as its value. How to convert list of lists into list -python, Why on earth are people paying for digital real estate? What is the Modified Apollo option for a potential LEO transport? If a has only one element, you can get it by: If it has more than one, then you need to specify how to get a number from more than one. Morse theory on outer space via the lengths of finitely many conjugacy classes. This can have application in data preprocessing domain. Are you going to fix the question to have the correct value of, python - Convert Single integer into a list, Why on earth are people paying for digital real estate? Not the answer you're looking for? I have a Python list which holds pairs of key/value: I want to convert the list into a dictionary, where multiple values per key would be aggregated into a tuple: Is there a more elegant, Pythonic solution for this task? Let's see each one by one. Here is an example of converting list to array: import numpy as np my_list = [1, 2, 3, 4, 5] my_array = np.array (my_list) print (my_array) # Output: [1 2 3 4 5] When are complicated trig functions used? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Maybe worth pointing out that this will only work if the sublists never have more than one item. Note that in Python 3 the str type does have the __iter__ attribute and this does not work: First, there is no general method that could tell a "single element" from "list of elements" since by definition list can be an element of another list. rev2023.7.7.43526. This can have application in data preprocessing domain. Not the answer you're looking for? The first IP_addr is Guaranteed. This is because the function concatenates a tuple of length 1 with the result of recursively calling itself on a list of length n-1, resulting in a tuple of length n. Each concatenation takes O(n) time, so the total time complexity is O(n^2). If the list is empty, return an empty tuple. Copy to clipboard # List of strings listOfStr = ["hello", "at" , "test" , "this" , "here" , "now" ] Now we want to create a dictionary with all elements in this list as keys. I've mentioned, the above code doesnt seem to work for if one of the nested lists is having a list of strings. If you want an int() you should cast it on each item in the list: That would also empty a and pop() off each back handle cases where they are strings. Merge two lists into one dict that may contain several values for each key, How to create a dictionary of lists from two columns in a dataframe, Making a dictionary from a list of strings (creating keys from the elements of the list), Convert a pair of list objects into dictionary with duplicates included, Remove the smallest element(s) from a dictionary, Python list to dict with multiple values for each key, Lists to dictionary but with multiple values for each key, How to convert a list into a multi value dictionary, Converting list of lists to a dictionary with multiple values for a key, Converting a list into a dictionary with key value pairs, How to convert a list with key value pairs to dictionary, Converting a list with multiple values into a dictionary, Converting a list to dictionary having key value pairs. How to convert a list of multiple integers into a single integer? Using lists instead of tuples as dict values: Using a plain dictionary is often preferable over a defaultdict, in particular if you build it just once and then continue to read from it later in your code: First, the plain dictionary is faster to build and access. I like Andrei Vajna's suggestion of hasattr(var,'__iter__'). You could also keep a untouched and just iterate over the items: Thanks for contributing an answer to Stack Overflow! Python Program to Convert a list of multiple integers into a single This is so useful that I wish it was part of the standard library. library has a tool that returns one item from an iterable. Brute force open problems in graph theory. Is there a distinction between the diminutive suffices -l and -chen? Alternately, you could use sys.version. Why not use lists consistently for all the variables? How can I remove a mystery pipe in basement wall and floor? Asking for help, clarification, or responding to other answers. How to Convert Python Dictionaries to (from) Lists, Strings, and Tuples Ask Question Asked 5 years, 9 months ago. A plain dictionary lets you explicitly state when you want to create a key-value pair, while the defaultdict always implicitly creates them, on any kind of access. English equivalent for the Arabic saying: "A hungry man can't enjoy the beauty of the sunset". To make this more readable, you can make a simple function: that's pretty neat and clever but I wouldn't use it because it's confusing to read. I want ot convert it into a normal integer. Are there ethnically non-Chinese members of the CCP right now? How do I merge multiple lists into one list? Because you are summing nested lists, you actually get [1,3]+[2,4] as a result of sum([[1,3],[2,4]],[]), which is equal to [1,3,2,4]. ( l is the list to flatten.) (Ep. Here, you should use indexes instead: When you do x[0:1], you're taking the list of items from the beginning of the list to the first interval. Why on earth are people paying for digital real estate? python - Convert Single integer into a list. What does "Splitting the throttles" mean? Python - Extract ith column values from jth column values. Convert List to Dictionary in Python: Simple Methods to Know I have a function whose input argument can either be an element or a list of elements. Can the Secret Service arrest someone who uses an illegal drug inside of the White House? 4 Answers Sorted by: 22 Use indexes You're slicing the list, which return lists. So, for simplicity and without actual loss of generality, say you have L sublists of I items each: the first I items are copied back and forth L-1 times, the second I items L-2 times, and so on; total number of copies is I times the sum of x for x from 1 to L excluded, i.e., I * (L**2)/2. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. :-), @DavidWaterworth: That silences the exception you'd get for passing a sequence with >1 item by silently collecting all the other items into. Or you can use itertools.chain.from_iterable() which doesn't require unpacking the list with the * operator: This approach is arguably more readable than [item for sublist in l for item in sublist] and appears to be faster too: Note from the author: This is very inefficient. Convert list to string in Python - 3 easy ways - Flexiple Tutorial If I had a nickel for every time some "known" behavior in production code turned out to be dead wrong Well, I probably wouldn't be. Create a list test_list with values [5, 6, 3, 8, 9] and a variable K with a value of 3. 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It's slower in the failure cases too (particularly when the iterable is too long), but those hardly matter (and the relative loss is much smaller, taking only 25-100% longer, not ~9x). numpy.asarray NumPy v1.25 Manual Is a dropper post a good solution for sharing a bike between two riders? Converting a list containing a single number into an integer, How to convert a single number into a single item list in python. rev2023.7.7.43526. To learn more, see our tips on writing great answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Why do complex numbers lend themselves to rotation? You can use the list extend method. Otherwise, take the first element of the list and put it in a new list. You can use ', '.join (list1) to join the elements of the list with comma and whitespace or ' '.join (to) to join with only white space. Use a for loop to iterate through the elements of the input list test_list. Time complexity: O(n), where n is the length of the input list.Auxiliary space: O(n), where n is the length of the input list. My code should work even if temp['IP_addr'].to_list() == []. Were Patton's and/or other generals' vehicles prominently flagged with stars (and if so, why)? This does not have keys. What is the significance of Headband of Intellect et al setting the stat to 19? If you are still interested in Python 2 compatibility, change, Doesn't work for unevenly nested lists like. "Flatten" list containing lists of lists to list of lists, Can I still have hopes for an offer as a software developer. Find centralized, trusted content and collaborate around the technologies you use most. The results show that if the iterable contains only a few inner iterables then sum will be fastest, however for long iterables only the itertools.chain.from_iterable, iteration_utilities.deepflatten or the nested comprehension have reasonable performance with itertools.chain.from_iterable being the fastest (as already noticed by Nico Schlmer). dictionary from a single list in python-1. Convert bytes to a string in python 3 - Stack Overflow Method 3: Using Dictionary Comprehension: Time Complexity: O(n), where n is the size of the input list.Auxiliary Space: O(n). Related. 7147. acknowledge that you have read and understood our. Why do complex numbers lend themselves to rotation? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. How does the theory of evolution make it less likely that the world is designed? Not the answer you're looking for? Asking for help, clarification, or responding to other answers. Pythonic way to get list element when expectation is that list contains only a single element? (Ep. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. How can I learn wizard spells as a warlock without multiclassing? Does being overturned on appeal have consequences for the careers of trial judges? If this argument is a single element then I put it in a list so I can iterate over the input in a consistent manner. Python String to Array - How to Convert Text to a List - freeCodeCamp.org Getting only element from a single-element list in Python? How much space did the 68000 registers take up? Can I ask a specific person to leave my defence meeting? [1, 2, [3, 4], [4], [], 9, 9.5, 'ssssss', ['str', 'sss', 'ss'], [3, 4, 5]] output:- [1, 2, 3, 4, 4, 9, 9.5, 'ssssss', 3, 4, 5], OP doesn't mention they want to use numpy. I created a solution using a simple embedded loop: I would suggest using generators with yield statement and yield from. Print the dictionary res which will have the key 8 and the value [5, 6, 3, 9]. The list should contain tuples where each tuple contains a key-value pair. Not a one-liner, but seeing all the answers here, I guess this long list missed some pattern matching, so here it is :). It gets more complicated if you want to support other 'list-like' data types, too, for example: or more generally, abstract away the question: but again, in summary, your method is simple and correct, which sounds good to me! Simply adding a mapping function for each element by map to the list, In here, there is a clear explanation of the drawback in terms of memory for this approach. I am working with an existing API so I can't change the input parameters. 4 Answers Sorted by: 9 a = a [0] print a 3 Or are you looking for sum? string.split(separator=None, maxsplit=-1) Let's break it down: string is the given string you want to turn into a list. python - Convert Single integer into a list - Stack Overflow 1. Convert list to a bunch of parameters. Cannot assign Ctrl+Alt+Up/Down to apps, Ubuntu holds these shortcuts to itself. (Ep. If the number of sublists is large, this performs a little worse than the above suggestion. this is a very inefficient way because of the quadratic aspect of the sum. rev2023.7.7.43526. Time Complexity: O(n)Auxiliary Space: O(n). Why did the Apple III have more heating problems than the Altair? Heads up: the OP edited the question to be completely different after this answer was posted. Travelling from Frankfurt airport to Mainz with lot of luggage. Why did Indiana Jones contradict himself? In this, we slice out the list on Kth index and assign as values in dictionary. 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6), Need to convert a list of strings to a list of normal numbers, strings are base 10, Convert single-element sub-lists to normal elements, Changing list as values in dict into normal value in dict, Identifying large-ish wires in junction box. A non-recursive function to flatten lists of lists of any depth: For a list containing multiple list here a recursive solution that work for me and that i hope is correct: Here's an approach I didn't see in the other answers. In this, we construct and iterate the list using list comprehension and finally convert the result list to tuple using tuple(). Why add an increment/decrement operator when compound assignnments exist? This includes lists, lists of tuples, tuples, tuples of tuples, tuples of lists and ndarrays. @RobCrowell Same here. Can I ask a specific person to leave my defence meeting? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The time complexity of this code is O(n), where n is the length of the input list test_list. To learn more, see our tips on writing great answers. If your list of lists comes from a nested list comprehension, the problem can be solved more simply/directly by fixing the comprehension; please see How can I get a flat result from a list comprehension instead of a nested list?. Making statements based on opinion; back them up with references or personal experience. Book or a story about a group of people who had become immortal, and traced it back to a wagon train they had all been on, Using Lin Reg parameters without Original Dataset. Print the result using the print() function and concatenation of string and tuple using the + operator. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. What is the Modified Apollo option for a potential LEO transport? The outer list is created using the list() constructor, which converts the list comprehension into a list. @VladimirVilimaitis As stated in answer, the code returns a generator, you can use it directly or create with it a sequence whose type is unrelated to the flattening process, it depends on your needs. If you want multiple elements returned as a tuple (not a list), you can enclose the whole statement: Is a dropper post a good solution for sharing a bike between two riders? rev2023.7.7.43526. I've tried to wonder around one line solution with only standad libraries. Why did the Apple III have more heating problems than the Altair? Python list comprehension to join list of lists. Thanks for contributing an answer to Stack Overflow! The resulting map object is then converted to a tuple using the tuple() function. Is religious confession legally privileged? You can do direct type comparisons using type(). In the case of one element, unpacking can not be used? It was a part of a function where I updated the values of a list constantly (list of lists with variable lengths). It doens't necessarily have to be pythonic. Finally, we can use the tuple() method to convert the list into a tuple. Doing x[0:2], for example, would return items 0 and 1. Making statements based on opinion; back them up with references or personal experience. Python : Convert list of lists or nested list to flat list - thisPointer Define a recursive function list_to_tuple_of_single_valued_lists which takes a list lst as an input. Can the Secret Service arrest someone who uses an illegal drug inside of the White House? That means a dictionary of Dictionaries has key and dictionary(as a value) pairs. Pythonic way to get the single element of a 1-sized list. Can a user with db_ddladmin elevate their privileges to db_owner. FYI, if flattening nested iterables is a common practice for you, there are some third-party packages that handle this well. I wanted a solution which can deal with multiple nesting ([[1], [[[2]], [3]]], [1, 2, 3] for example), but would also not be recursive (I had a big level of recursion and I got a recursion error. 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6), python function that iterates over list or, in case of int, just takes int, Is there a way to convert a string to a list, python convert a string to arguments list, Python way to convert argument list to string, turn string containing arguments into an array with python, How to make it one-liner? 587), The Overflow #185: The hardest part of software is requirements, Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Temporary policy: Generative AI (e.g., ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6). Thinking in terms of types, the original variable you have is of type List[int] ([1, 2, 3]).. let's see the example. Why do keywords have to be reserved words? Modified 2 years, 4 months ago. For qualitative reasoning: Lower is better. I kept looking here every time I wanted to flatten a list, but this gif is what drove it home: @TimDierks: I'm not sure "this requires you to understand Python syntax" is an argument against using a given technique in Python.
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