I imagine I could write a function to unpack the values, however I'm wondering if there is a simple built-in way of converting a dataframe to a series/list? (l is the list to flatten.). Are the keys already sorted in the input list? dictionary from a single list in python-1. Connect and share knowledge within a single location that is structured and easy to search. matplotlib.cbook.flatten() will work for nested lists even if they nest more deeply than the example. [leaf for tree in forest for leaf in tree] might be easier to comprehend and apply. Both versions will work on arbitrary hierarchy nested lists, and exploits language features (Python3.5) and recursion. library has a tool that returns one item from an iterable. One such problem can be converting List elements to single values lists in tuples. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, There may be alternatives, but there's usually only one. @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. Modified 2 years, 4 months ago. Only if your data contains integer values: Thanks for contributing an answer to Stack Overflow! I'm just adding a special case here for anyone who is struggling like I was with list comprehensions, which return a list. A+B and AB are nilpotent matrices, are A and B nilpotent? How do you find the first key in a dictionary? That is an ok way to do it (don't forget to include tuples). The inner lists are created using a generator expression that iterates over the original list and creates a new list containing a single integer. Morse theory on outer space via the lengths of finitely many conjugacy classes. I just don't support a claim that importing a function, and intentionally misusing it to get a benefit by side-effect from the misuse, is "Arguably less awkward and PEP-compliant" than literally any other solution out there. It shows to be the fastest: There are several answers with the same recursive appending scheme as below, but none makes use of try, which makes the solution more robust and Pythonic. 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. Typo in cover letter of the journal name where my manuscript is currently under review. What is the verb expressing the action of moving some farm animals in a field to let them eat grass or plants? Asking for help, clarification, or responding to other answers. Why not use lists consistently for all the variables? order{'C', 'F', 'A', 'K'}, optional Memory layout. Converting a list to string (method #1) in the first method, we'll onvert alist to string without using any built-function. How to convert List from column to list of DataFrame? 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. 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. Do I have the right to limit a background check? Another unusual approach that works for hetero- and homogeneous lists of integers: np.flatten also accepts other parameters: More details about parameters are available here. This can have application in data preprocessing domain. This kind of problem can have applications in data domains. Is there any potential negative effect of adding something to the PATH variable that is not yet installed on the system? Why on earth are people paying for digital real estate? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. If you want multiple elements returned as a tuple (not a list), you can enclose the whole statement: Can the Secret Service arrest someone who uses an illegal drug inside of the White House? This does not have keys. (Ep. How to convert list of lists into list -python, Why on earth are people paying for digital real estate? Nice not to use stack, but it has very bad time complexity. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Would it be possible for a civilization to create machines before wheels? Following your current approach, you can flatten your array before converting it to a 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. Can I contact the editor with relevant personal information in hope to speed-up the review process? You can use a list comprehension, the itertools library, or simply loop through the list of lists adding each item to a separate list, etc. This is stacking a lot of random garbage to get a result through, essentially, API misuse. >>> a= [1] >>> sum (a) 1 >>> a= [1,2,3] >>> sum (a) 6 Share Improve this answer Follow answered Jan 28, 2010 at 5:03 YOU 120k 34 186 219 Add a comment 2 To learn more, see our tips on writing great answers. Method #6: Using list() + tuple() + generator expression. Python: Convert a list into a normal value - Stack Overflow This method is relatively efficient and quite compact: In Python3 this becomes (making exports explicit): Note that reduce has moved to functools and that lambdas no longer accept tuples. This is probably the most general requirement for a list-like type than only checking the type. Question: why do you have inconsistent data types in the first place? By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. 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. That means a dictionary of Dictionaries has key and dictionary(as a value) pairs. Connect and share knowledge within a single location that is structured and easy to search. How much space did the 68000 registers take up? How to add values to a dictionary from a list with same key values in Python? Answers that can handle greater depth of nesting are more likely to be useful to someone who finds this question. Thanks for contributing an answer to Stack Overflow! What does that mean? 1. Therefore, at the root, a flat list is returned. Finally, we can use the tuple() method to convert the list into a tuple. re: proper. Wrap that list in a tuple, and concatenate the tuple with the result of recursively calling list_to_tuple_of_single_valued_lists on the rest of the list. 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 zip magic for classes instead of tuples, Travelling from Frankfurt airport to Mainz with lot of luggage, Cultural identity in an Muti-cultural empire. rev2023.7.7.43526. 7147. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. rev2023.7.7.43526. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Can I still have hopes for an offer as a software developer, Book set in a near-future climate dystopia in which adults have been banished to deserts. Here is an example: my_list = [ ('a', 1), ('b', 2), ('c', 3)] my_dict = dict (my_list) print (my_dict) # Output: {'a': 1, 'b': 2, 'c': 3} This creates a tuple of tuples where each inner tuple contains a single integer from the original list. 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. [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. it fails when all elements are not list. What is the Modified Apollo option for a potential LEO transport? Would a room-sized coil used for inductive coupling and wireless energy transfer be feasible? Connect and share knowledge within a single location that is structured and easy to search. Curiosity alone. 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. @ShadowRanger Thanks for the feedback. For lists of lists of lists, you'll need another solution. How to Properly Convert a List to a String in Python - PyTutorial Time Complexity:The time complexity of the list_to_tuple_of_single_valued_lists function is O(n^2), where n is the length of the input list. rev2023.7.7.43526. Can you work in physics research with a data science degree? What is the verb expressing the action of moving some farm animals in a field to let them eat grass or plants? Time complexity: O(n), where n is the length of the input list.Auxiliary space: O(n), to store the output list. This kind of problem can have applications in data domains. At end, the result is converted back to tuple using tuple(). Method 5: Using filter and lambda function. python - list to dictionary conversion with multiple values per key x[-1] = will give you the last element of the list. (Ep. In this, we construct and iterate the list using list comprehension and finally convert the result list to tuple using tuple(). In the case of obj = [[1, 2,], [3, 4], [5, 6]], all of the solutions here are good, including list comprehension and itertools.chain.from_iterable. Is a dropper post a good solution for sharing a bike between two riders? rev2023.7.7.43526. Find centralized, trusted content and collaborate around the technologies you use most. Why free-market capitalism has became more associated to the right than to the left, to which it originally belonged? 1. declaring an empty variable. Sure, complex usage could confuse, but the "splat" operator is generally useful in many circumstances, and this isn't using it in a particularly obscure way; rejecting all language features that aren't necessarily obvious to beginning users means you're tying one hand behind your back. 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. dtypedata-type, optional By default, the data-type is inferred from the input data. 3 Answers Sorted by: 10 create_list is building a list of all the items in the str ing form of data. string.split(separator=None, maxsplit=-1) Let's break it down: string is the given string you want to turn into a list. Brute force open problems in graph theory. acknowledge that you have read and understood our. This seems like a reasonable way to do it. In this, we perform task of extending logic of conversion to each element using map(), and list conversion to each element using zip(). 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). This function works whatever the size of the lists: Dictionary needs key and value pairs. To have list members each be its own key and value: dict(zip(list, list)). Book set in a near-future climate dystopia in which adults have been banished to deserts. How to convert columns and values of DataFrame to one list? Print the original list and the resulting dictionary. This is 18x faster than underscore._.flatten: It only works when sublists have identical dimensions. Let's discuss certain ways in which this task can be performed. Convert the input to an array. Thanks for contributing an answer to Stack Overflow! @Bharel: Okay, so as long as we're agreed that's batshit insane, we're good. Connect and share knowledge within a single location that is structured and easy to search. Book set in a near-future climate dystopia in which adults have been banished to deserts. Can I ask a specific person to leave my defence meeting? Making statements based on opinion; back them up with references or personal experience. Can I ask a specific person to leave my defence meeting? It ships with an implementation for flatten (source, from the itertools recipes): Note: as mentioned in the docs, flatten requires a list of lists. Why do complex numbers lend themselves to rotation? Non-definability of graph 3-colorability in first-order logic. list to dictionary conversion with multiple values per key? also, mind that list of strings will be flattened to a list of characters. I am curious on what an efficient/pythonic implementation would be for converting a single item list to a string. I want to concatenate them such that I get the following: This is because of the a term. How does the theory of evolution make it less likely that the world is designed? Convert list to string in Python - 3 easy ways - Flexiple Tutorial Unfortunately no. How much space did the 68000 registers take up? 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. Find centralized, trusted content and collaborate around the technologies you use most. You can do direct type comparisons using type(). Perhaps below code could solve the issue with satisfying quality (for the python3): Thanks for contributing an answer to Stack Overflow! Do I remove the screw keeper on a self-grounding outlet? Remove the element at index K from test_list using the pop() method and store its value in a variable called key. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. The outer list is created using the list() constructor, which converts the list comprehension into a list. 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? Is a dropper post a good solution for sharing a bike between two riders? This article is being improved by another user right now. Doing x[0:2], for example, would return items 0 and 1. Asking for help, clarification, or responding to other answers. I've tried to wonder around one line solution with only standad libraries. How to create dictionary from list. I created a solution using a simple embedded loop: I would suggest using generators with yield statement and yield from. How alive is object agreement in spoken French? Why do complex numbers lend themselves to rotation? By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Time complexity: O(n)Auxiliary space: O(n). What does "Splitting the throttles" mean? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How to convert an integer to a list in python? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I need to convert a list of lists (containing strings) into a simple list of integers. 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. Sci-Fi Science: Ramifications of Photon-to-Axion Conversion. Adding another variation. In this, we slice out the list on Kth index and assign as values in dictionary. d contains now {1: ('A', 'B'), 2: ('C',)}. Asking for help, clarification, or responding to other answers. Time complexity: O(N)Auxiliary space: O(N). Viewed 17k times 13 Say I have the following lists: a = 1 b = [2,3] c = [4,5,6] I want to concatenate them such that I get the following: . What is the Modified Apollo option for a potential LEO transport? Therefore, the space required is proportional to the size of the input list. Create a list comprehension that creates a list of lists where each inner list contains a single integer from the original list. My manager warned me about absences on short notice. For each element ele in test_list, create a new list [ele] containing the single value. Why did the Apple III have more heating problems than the Altair? The first one is unique in that it also raises if the list contains more than one element. 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). As the join () methods only take in string values, we use the map () methods to convert the integer values into a string before converting the list to a string. why isn't the aleph fixed point the largest cardinal number? You can still return x from lambda, using something like this: Note: extend is more efficient than + on lists. Preferred way of unpacking a single element iterable in Python. Why do keywords have to be reserved words? To flatten a data-structure that is deeply nested, use iteration_utilities.deepflatten1: It's a generator so you need to cast the result to a list or explicitly iterate over it. Define a recursive function list_to_tuple_of_single_valued_lists which takes a list lst as an input. Why free-market capitalism has became more associated to the right than to the left, to which it originally belonged? 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(Ep. Asking for help, clarification, or responding to other answers. You can use the list extend method. It is just an integer. Getting only element from a single-element list in Python? Is there a distinction between the diminutive suffices -l and -chen? Time complexity: O(n), where n is the length of the original list, since it involves a single loop through the list to extract the element at position K.Auxiliary space: O(n), since it involves creating a dictionary with a single key-value pair and a list with n-1 elements. Can the Secret Service arrest someone who uses an illegal drug inside of the White House? Python : How to convert a list to dictionary - thisPointer 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Note these results from some typical Python types: This has the added advantage of treating a string as a non-iterable - strings are a grey area, as sometimes you want to treat them as an element, other times as a sequence of characters. I have. Using functools.reduce, which adds an accumulated list xs to the next list ys: Here is a general approach that applies to numbers, strings, nested lists and mixed containers. @DavidWaterworth: That silences the exception you'd get for passing a sequence with >1 item by silently collecting all the other items into _ (making an empty list there if it's in fact single element); it's otherwise identical to singleitem, = mylist. d1 is a temporary defaultdict with lists as values, which will be converted to tuples in the last line.