Flatten an irregular (arbitrarily nested) list of lists, rightfootin.blogspot.com/2006/09/more-on-python-flatten.html, joelonsoftware.com/articles/fog0000000319.html, mathieularose.com/how-not-to-flatten-a-list-of-lists-in-python, Why on earth are people paying for digital real estate? Pythonic way to get the single element of a 1-sized list. 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. I have. Flattening it is easy with itertools.chain. What is the proper way to iterate through a list with one item in python? What does that mean? Other than Will Riker and Deanna Troi, have we seen on-screen any commanding officers on starships who are married? Use the tuple() method to convert the list res into a tuple res_tuple. How do I convert a tuple of tuples to a one-dimensional list using list comprehension? Book set in a near-future climate dystopia in which adults have been banished to deserts. This can have application in data preprocessing domain. Were Patton's and/or other generals' vehicles prominently flagged with stars (and if so, why)? Print the result using the print() function and concatenation of string and tuple using the + operator. 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. 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. What would stop a large spaceship from looking like a flying brick? In addition, more_itertools.one raises an error if the iterable is empty or has more than one item. six is also a third-party package, though it is stable. Let's discuss certain ways in which this task can be performed. critical chance, does it have any reason to exist? How to passive amplify signal from outside to inside? That means a dictionary of Dictionaries has key and dictionary(as a value) pairs. Asking for help, clarification, or responding to other answers. English equivalent for the Arabic saying: "A hungry man can't enjoy the beauty of the sunset". What does that mean? 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. When and why does the interpreter unravel by assuming same length sublists? How to convert a list of multiple integers into a single integer? Not the answer you're looking for? In Python, a negative list index means: start indexing from the right of the list in direction to the left, where the first position from right-to-left is -1, the second position is -2 and the last position is -len(lst). input is a huge open file) and I'd suggest an auxiliary generator instead: now in every single one of your functions needing such argument normalization, you just use: You can use an auxiliary normalizing-function even in the other case (where you need a real list for further nefarious purposes); actually, in such (rarer) cases, you can just do: so that the (inevitably) somewhat-hairy normalization logic is just in ONE place, just as it should be!-). However, you may also want to consider if the argument has a __iter__ method or __getitem__ method. I just prefer to program defensively, so violations of requirements don't pass silently (sure it fails, but it fails loudly, which is much easier to identify and fix than subtle misbehaviors). How to play the "Ped" symbol when there's no corresponding release symbol. d contains now {1: ('A', 'B'), 2: ('C',)}. How to Properly Convert a List to a String in Python - PyTutorial How to play the "Ped" symbol when there's no corresponding release symbol, How to disable (or remap) the Office Hot-key. 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. You need to check whether the value is a list or not: x[0] = will give you 0th index of the list, first value. You can do direct type comparisons using type(). Conversion of data types is the most common problem across CS domain nowdays. this is a very inefficient way because of the quadratic aspect of the sum. is faster than the shortcuts posted so far. I think the way around for this may be creating a gloabl flist, like below. x[-1] = will give you the last element of the list. What is the Modified Apollo option for a potential LEO transport? Connect and share knowledge within a single location that is structured and easy to search. Nov 30, 2020 at 11:46. This new list is stored in the variable res. I want to concatenate them such that I get the following: This is because of the a term. this kind of direct comparison isn't a great idea - if a user subclasses. :P, This doesn't work for him because he said he can't change the arguments and someone could enter [1,2] and it would be doubly wrapped as ([1,2],). This answer is already up in this question: Will also give a TypeError if your list contains a tuple. Initialize the original list test_list and the index K. Create a set keys with the element at index K in test_list. How alive is object agreement in spoken French? Can I ask a specific person to leave my defence meeting? 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). There are multiple approaches possible to convert the given list into a single integer. In particular, the new code is slower by the greatest margin for the success case (which is presumably the common case); in 3.11.1, the original implementation takes around 41 ns on a one-tuple on my machine, while the new one takes 348 ns. Making statements based on opinion; back them up with references or personal experience. Morse theory on outer space via the lengths of finitely many conjugacy classes, My manager warned me about absences on short notice. rev2023.7.7.43526. Can Visa, Mastercard credit/debit cards be used to receive online payments? The reason your function didn't work is because the extend extends an array in-place and doesn't return it. Asking for help, clarification, or responding to other answers. critical chance, does it have any reason to exist? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Note that only works on lists of lists. If you are willing to give up a tiny amount of speed for a cleaner look, then you could use numpy.concatenate().tolist() or numpy.concatenate().ravel().tolist(): You can find out more here in the documentation, numpy.concatenate and numpy.ravel. @Bharel: Okay, so as long as we're agreed that's batshit insane, we're good. See below on flattening more irregular inputs. Are there ethnically non-Chinese members of the CCP right now? How can I get a flat result from a list comprehension instead of a nested list? 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. Python - Convert Lists into Similar key value lists dtypedata-type, optional By default, the data-type is inferred from the input data. 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. How to convert an integer to a list in python? This method converts lists to strings in python using the map () and join () functions. Remove the element at index K from test_list using the pop() method and store its value in a variable called key. You need to do two things with your list flatten it out and then convert the strings to int. - DanielBell99. Both versions will work on arbitrary hierarchy nested lists, and exploits language features (Python3.5) and recursion. If you are still interested in Python 2 compatibility, change, Doesn't work for unevenly nested lists like. Why not use lists consistently for all the variables? Asking for help, clarification, or responding to other answers. Is there any potential negative effect of adding something to the PATH variable that is not yet installed on the system? Ha! The outer list is created using the list() constructor, which converts the list comprehension into a list. For qualitative reasoning: Lower is better. How should I select appropriate capacitors to ensure compliance with IEC/EN 61000-4-2:2009 and IEC/EN 61000-4-5:2014 standards for my device? Also, just to be clear, this solution. 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. Time Complexity: O(n)Auxiliary Space: O(n). 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. Can the Secret Service arrest someone who uses an illegal drug inside of the White House? The array () function creates a new NumPy array from the elements of the given list. 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. 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. 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? In this approach, the map() function is used to apply a lambda function to each element of the original list. tuple([el for el in l if (el==5 or el==6)]). This can flatten both simple and complicated containers (see also Demo). Time complexity: O(n), where n is the length of the input list.Auxiliary space: O(n), to store the output list. (Ep. To learn more, see our tips on writing great answers. 3 Answers Sorted by: 10 create_list is building a list of all the items in the str ing form of data. This creates a tuple of tuples where each inner tuple contains a single integer from the original 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). It was a part of a function where I updated the values of a list constantly (list of lists with variable lengths). Are the keys already sorted in the input list? python - How do I make a flat list out of a list of lists? - Stack Overflow python - How to convert list to string - Stack Overflow The above one creates several local lists and returns them which are used to extend the parent's list. Ask Question Asked 5 years, 9 months ago. Does being overturned on appeal have consequences for the careers of trial judges? 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. number of arrays by average size of array? This kind of problem can have applications in data domains. In this, we slice out the list on Kth index and assign as values in dictionary. Convert List to Dictionary in Python: Simple Methods to Know What is the verb expressing the action of moving some farm animals in a field to let them eat grass or plants? How to create dictionary from list. (Ep. This includes lists, lists of tuples, tuples, tuples of tuples, tuples of lists and ndarrays. Create a dictionary called res with the key key and the value test_list. Not the answer you're looking for? Invitation to help writing and submitting papers -- how does this scam work? How do I make a flat list out of a list of lists? This answer creates a string in which the list elements are joined together with no whitespace or comma in between. 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. I will add that the more_itertools You can use the list extend method. 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. 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). There's an in-depth discussion of this here: I found the syntax hard to understand until I realized you can think of it exactly like nested for loops. This is a dead-simple example: Adding a subscript extracts the element from the list. It takes two optional parameters. I am working with the lxml api, specifically xpath which returns a list of Element s. Assuming I have the following xml. Pythonic way to take the only item from a list, Iterating over only a part of list in Python, Pythonic way to unpack an iterator inside of a list, Extracting only one element from the list that i have created, Retrieving all but one elements in a list of lists (Python), Python list comprehension: Unlist if list contains only one element, Cultural identity in an Muti-cultural empire, Python zip magic for classes instead of tuples. How to flatten mixed dimensional array into a two dimensional list? Non-definability of graph 3-colorability in first-order logic. How to convert list of lists into list -python Ask Question Asked 3 years, 7 months ago Modified 10 months ago Viewed 10k times 3 I need to convert a list of lists (containing strings) into a simple list of integers. Not the answer you're looking for? The recursion goes down until it finds a non-list element, then extends the local variable flist and then rolls back it to the parent. Connect and share knowledge within a single location that is structured and easy to search. [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. Making statements based on opinion; back them up with references or personal experience. The neuroscientist says "Baby approved!" I created a solution using a simple embedded loop: I would suggest using generators with yield statement and yield from. A+B and AB are nilpotent matrices, are A and B nilpotent? Show 17 more comments. python - Converting a one-item list to an integer - Stack Overflow Heads up: the OP edited the question to be completely different after this answer was posted. 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). Thus preventing the any derived types from accidentally being wrapped. Convert list of integers to an integer python. 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. This is so useful that I wish it was part of the standard library. lst=[1, [2,3]]). This is because we need to iterate over the input list once to create the new list new_list using a list comprehension, which takes O(n) time.Auxiliary space: O(n) because we create a new list new_list which has n-1 elements, and a dictionary with one key-value pair.
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python convert list to single value
