Find index of element in list python numpy. In this example the element is 2.

Find index of element in list python numpy. Jan 1, 2025 · Learn how to find the index of an element in a Python array (or list) using methods like `index ()`, loops, and NumPy's `where ()`. The first array returned contains the indices along axis 1 in the original array, the second array contains the indices along axis 2. Jun 16, 2021 · So I have a numpy array containing lists (of various lengths) which consist of strings. Whether you‘re working with numerical data, text-based information, or a mix of different data types, the ability to quickly and Jul 12, 2025 · We are given a list we need to find all indexes of Non-Zero elements. Call the numpy. Index the same ndarray multiple times efficiently # It must be kept in mind that basic indexing produces views and advanced indexing produces copies, which are computationally less efficient. First we convert the given list to an array. argmax. Then, we can Mar 31, 2021 · Example: In the below example, the array elements contain a NULL value passed using numpy. Notes isin is an element-wise function version of the python keyword in. 2 Given it returns a list of indices, is there any way in numpy to coalesce those indices into a minimal list of slices. where () method is used to specify the index of a particular element specified in the condition. @thefourtheye But they are both built-in methods, which means they iterate over the list much faster than a python loop. In this example, numpy. It contains various features. sparseboolean, optional Return a Nov 13, 2023 · 3) Using Numpy module The Numpy library also allows us to find an index of any element in a list using its pre-built function np. Find absolute difference with K of each element, and return the minimum from it. Would still love to see something that's a NumPy equivalent to VLOOKUP, or even a Pandas merge. partition. Apr 10, 2021 · How to find the index of an element in an numpy array? Asked 3 years, 11 months ago Modified 3 years, 11 months ago Viewed 226 times Jul 15, 2025 · Sometimes we need to find out the indices of all null elements in the array. If your data is sorted, you can use numpy. numpy. As a data scientist working with large datasets, I often need to find the nearest value to a given target within an array. We can create a new list of the previous elements with their counter variables as tuples in a list using list comprehension. find_nearest(array, value) numpy. Here, we delve deep into various techniques you can employ to find an element in a Python list. Initialize the list test_list with some values Aug 16, 2023 · The index () is a built-in function in Python that can be used to search the element from the list and return the position of the element. I am not interested in the following answers because they scan the whole array and don't sto Finding the first element in a 2-D list can be rephrased as find the first column in the 2d list. It returns an enumerate type object, which is iterable. Determine the value of k. We can use the nsmallest () function from the heapq module to find the smallest K elements and their indices in a list. Assuming that a is sorted: Mar 12, 2019 · Given numpy array, the task is to find elements within some specific range. Jul 12, 2025 · In this article, we will cover the Indexing of Multi-dimensional arrays in Python using NumPy. where() checks where the condition arr > 20 is true, and returns the indices [3, 4], meaning the elements at index 3 and 4 (25 and 30) are greater than 20. Jun 30, 2013 · Fastest to slowest execution speeds with 32-bit Python 2. index(2. start, endarray_like, with any integer dtype Oct 3, 2011 · How can I find the index of the first occurrence of a number in a Numpy array? Speed is important to me. Let's explore some more ways to perform element indices summation in Python. What is the most efficient way to obtain the indices of the elements that do have a value of zero? Mar 14, 2012 · 1 Keep in mind that if space isn't important you can sort any list without moving the contents by creating a secondary list of the sorted indices. ndim) ndarray Indices of elements that are non-zero. array ( [1, 3, 5, 6, 9, 10, 14, 15, 56]) I would like to find all the indexes of the elements within a specific range. Feb 7, 2024 · This article explains how to get and set values, such as individual elements or subarrays (e. For example. abs (d) function, with d as the difference between the elements of array and x, and store the values in a different array, say difference_array []. NumPy is a general-purpose array-processing package. How to find the index of value in Numpy array using numpy. Stack Overflow - Where Developers Learn, Share, & Build Careers Jan 3, 2011 · NumPy has the efficient function/method nonzero() to identify the indices of non-zero elements in an ndarray object. The heapq module provides the implementation of heap queue algorithm. aa = range(-10,10) Find position in aa where, the value 5 gets exceeded. The reason for this is because is checks are lightning fast (pointer comparisons) and since it's fairly common to search for something in a list that you already have a reference to, python does an is comparison before falling back to the == comparison. Apr 14, 2025 · NumPy has argmax and argmin functions which can be used to find the indices of the maximum and minimum element. array (test_list). It also returns all indexes of occurrence for that element. We can then use numpy's where function to get the indices of the True elements, which will give us the indices of the odd elements. May 25, 2025 · The Importance of Mastering List Index Retrieval In the world of Python, lists are one of the most versatile and widely-used data structures. The indexes in NumPy arrays start with 0, meaning that the first element has index 0, and the second has index 1 etc. It’s possible to access an array element by passing its index position. I have a numpy array of numbers, for example, a = np. And the stored elements are identified by an index value. The values element [isin] are in test_elements. It leverages C-level optimizations under the hood, making it a great choice for data science or performance-critical applications. Approach: Create a NumPy array. Whether you prefer using built-in functions like max() and index(), using of the numpy library with argmax() function, or using list comprehensions. Most of the following examples show the use of indexing when referencing data in an array. You also learned how to use the numpy where() function to do and the more_itertools locate() function. I am using Jupyter Notebook for Python 3 and have the following code illustrated below: Are you looking for elements in list_2 that appear nowhere in list_1 or elements in list_2 that are not present at the same index in list_1? Jan 18, 2025 · In this introduction to NumPy, you'll learn how to find extreme values using the max() and maximum() functions. 000x Apr 17, 2023 · Approach 3: Using numpy Note: Install numpy module using command "pip install numpy" The numpy. Using a Loop A manual approach involves using a loop to iterate through the list and collecting indices where the element matches. Syntax : numpy. Using List Comprehension List comprehension can be used to find the indices of non-zero elements by iterating through the list with enumerate (). Examples: Input: [1,3,5,2,4,6] k = 3 Output: [1,2,3] Method 1: Using np. where # numpy. NumPy specifies the row-axis (students) of a 2D array as “axis-0” and the column-axis (exams) as axis-1. Get the indices where the array elements are not None: non_none_indices = np. npi. It is the fundamental package for scientific computing with Python. sort () . The while-loop in this answer is the fastest implementation tested. I would like a similar thing, but returning the indexes of the N maximum values. in1d (), which is an element-wise function version of the python keyword in. NumPy Apr 25, 2012 · So far I don't see any need for numpy; you can make use of defaultdict, provided that you memory is sufficient, it should be if number of observation is not too many millions. Here is the code for this function: I want to ask a question about finding the position of an element within an array in Python's numpy package. However it's true that senshin could have just used sublist. It is immensely useful in data processing where decisions need to be based on criteria, helping to extract or manipulate data efficiently. where () but for that, you need to first convert your list into a numpy array using np. To search an array, use the where() method. 7. Step-by-step examples included In this tutorial, we will look at how to find the index of an element in a numpy array. np. 667560 secs, rel speed 1. argmax () quickly returns the index of the maximum element in a list or NumPy array. There’s an answer using np. E. index(element) However, it doesn't work when there are two of the same numbers, as in the first example above, which returns 0 because -2 is in both the 0th and 1st position of the list. sparseboolean, optional Return a Jul 4, 2025 · Then, a. 0] I would like to find the location of the first number in the list that is not equal to zero. Python doesn't have a specific data structure to represent arrays. I'm simply trying to find like values in 2 arrays. Parameters: dimensionssequence of ints The shape of the grid. Dec 20, 2020 · How to find the index of a list element in a numpy array using ranges Asked 4 years, 3 months ago Modified 4 years, 3 months ago Viewed 178 times I have a numerical list: myList = [1, 2, 3, 100, 5] Now if I sort this list to obtain [1, 2, 3, 5, 100]. where( array==0). Jul 23, 2025 · Explanation: enumerate (a) generates pairs of indices and elements. Also bear in mind that if you are doing this look up just once, then you will just have to traverse every element in the list O (n). They allow you to store and manipulate collections of items, making them essential for a vast array of programming tasks. Returns: index_array(N, a. array([[1,2,3], [4,5,6], [7,8,9]]) >>> np. myList. Jan 7, 2015 · I have two numpy arrays and I'd like to get the indices of all elements in the first array that are in the second array. where(condition Apr 10, 2024 · When only a condition is provided, the numpy. Searching Arrays You can search an array for a certain value, and return the indexes that get a match. For example: import numpy as np x = np. Mar 11, 2025 · In this tutorial, we will explore various methods to find the first index of an element in a NumPy array using Python. Import the numpy module using the import statement. It provides a high - performance multidimensional array object and tools for working with these arrays. What is a good way to find the index of an element in a list in Python? Note that the list may not be sorted. Aug 17, 2011 · To check multiple values, you can use numpy. With numpy I am using the below algorithm to find the index of an element of a list in a separate list IndexList = np. Jul 15, 2025 · In this article, let us see how to find the k number of the smallest values from a NumPy array. What I want is the indices of the elements from the original list in the sorted order i. argmax() function in Python is a powerful tool within the NumPy library, designed to return the indices of the maximum values along the specified axis. array (a)>4 gives a bool array with all the elements that should be kept And X is filtered by the bool array so only the elements where a is greater than 4 are selected (and the rest discarded) Access Array Elements Array indexing is the same as accessing an array element. arra Feb 20, 2024 · Using np. Space Complexity: O (k), where k is the number of elements greater than 10 in the input list. Jul 23, 2025 · We can use an index () method or a simple for loop to accomplish this task. Apr 8, 2023 · Import the numpy library: import numpy as np Convert the list to a numpy array: arr = np. Jun 2, 2013 · Is there a built-in function or a very simple way of finding the index of n largest elements in a list or a numpy array? K = [1,2,2,4,5,5,6,10] Find the index of the largest 5 elements? Jul 23, 2025 · Index of nearest value: 3 Approach to Find the nearest value and the index of NumPy Array Take an array, say, arr [] and an element, say x to which we have to find the nearest value. 0, 0. May 1, 2023 · Time Complexity: O (n), where n is the length of the input list as we are iterating through the list. It returns the index of the first occurrence of the element we are looking for. array ( [0,1,1,2,3,4,5,5]) y = np. Aug 19, 2022 · How to Access the First Element of a Numpy Array Numpy arrays follow traditional Python indexing. Note: For more information, refer to Python The other answers give fine solutions when working in pure python. Syntax: numpy. Jan 23, 2024 · NumPy is a powerful library for numerical computing in Python, widely used in the fields of data analysis, machine learning, scientific computing, and more. The code uses np. . : master array is [1,2,3, I have two 1D arrays, x &amp; y, one smaller than the other. The idea is simple: records_array is a numpy array of timestamps (datetime) from which we want to extract the indexes of repeated numpy. array ( [1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3 numpy. This creates a new numpy array from the original list. Aug 2, 2011 · NumPy proposes a way to get the index of the maximum value of an array via np. array probably makes using Dec 30, 2024 · Introduction The numpy. Sep 17, 2021 · This tutorial explains how to find the index location of specific values in a NumPy array, including examples. argmin but it gives me the index of very first minimum value in a array. We’ll cover straightforward techniques that allow you to quickly retrieve the desired index, making your coding experience smoother and more efficient. 6 -> 1,000,000 executions, best of 3) mmtauqir - first occurrence : 0. I see that the correction @atomh33ls and I propose leads to the index of the largest element (s) of the array, while the OP was asking about the largest elements along a certain axis. isin(a, b) is roughly equivalent to np. For example, max(my_list) returns the maximum element in the list, and index() is then used to find its index. Alternatively, you can use a for loop. searchsorted (): The function is used to find the indices into a sorted array arr such that, if elements are inserted before the indices, the order of arr would be still preserved. I covered a few important methods such as using the max() function with the index() method, iterating over the list with enumerate(), and utilizing the numpy. I've found two naive ways to do this, the first is slow, and the second memory- @MadPhysicist -- it turns out that if you use the same array, numpy python will do the right thing. The examples work just as well when assigning to an array. I'd like to find all rows where a certain string appears in, e. find(a, sub, start=0, end=None) [source] # For each element, return the lowest index in the string where substring sub is found, such that sub is contained in the range [start, end). Let's discuss certain ways to get indices of true values in a list in Python. Method 1: Finding indices of null elements using numpy. Using numpy. min (test_list), which returns a Boolean array with True at the indices where the elements are equal to the minimum element in the list, and False elsewhere Jul 11, 2025 · Basic Usage Without x and y If only the condition is provided, numpy. max() which is a boolean array with the only non-zero element at (0,9). Jun 4, 2022 · We use lists in a python program to store different types of objects when we need random access. but the output is a tuple of size 2 and each item of it is a numpy array and I do not how can I find the first index of occurring zero in this array. Indexing on ndarrays — NumPy v1. We can handle this using a try and except block. I would like to find the nearest value for the target value. a = np. Method 4: Using List Comprehension Although less efficient for larger arrays, list comprehension offers a Pythonic way to filter elements in a numpy array. Apr 12, 2024 · A step-by-step illustrated guide on how to get the indices of the N largest values in a NumPy array in multiple ways. So how to get the index of the last non-zero element of a list, even when there are elements with the same value? May 5, 2023 · In this method to obtain the indices of the smallest K elements in a list can be to use the heapq module in Python. If the list is short it's no problem making a copy of it from a Python list, if it isn't then perhaps you should consider storing the elements in numpy array in the first place. It provides a high-performance multidimensional array object and tools for working with these arrays. where(condition, [x, y, ]/) # Return elements chosen from x or y depending on condition. It is particularly helpful in data-processing contexts where identifying the presence and location of non-zero elements can indicate significant data points or features. 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. Suppose I have a numpy array of the form: arr=numpy. where() and argsort+searchsorted() function on 1 and 2 dimensional array. Apr 19, 2023 · Here is another approach using the numpy module. Thanks! Feb 2, 2024 · Python list has a built-in method called index(), which accepts a single parameter representing the value to search within the existing list. index (res) returns its index, which is 5 since indexing starts at 0. argmin(a) This gives me 0, instead I am expecting, 0,5,7. 8 and the index is 5. Jul 12, 2025 · Explanation: The list comprehension [arr [i] for i in indices] extracts elements at the given indices. where(arr == 6) (array([1], dtype=int64), array([2], dtype=int64)) The first array in the output Nov 6, 2024 · Explore the top methods to quickly locate the first index of a specific value in a Numpy array, focusing on performance and efficiency. Sort the array in ascending order using the sort () method. How to determine the index of all matching elements in a list? - Using for loop & enumerate() function vs. Dec 5, 2024 · Explore various techniques in Python to find indices of all occurrences of a specific element in a list, including numpy methods and custom functions. On the other hand, what I am thinking of doing is similar but different. 18 with numpy version 1. Method #2 : Using list comprehension + enumerate () The combination of these two function can also perform this particular task efficiently and in one May 9, 2017 · Assuming that I have a numpy array such as: import numpy as np arr = np. Note NumPy slicing creates a view instead of a copy as in the case of built-in Python sequences such as string, tuple and list. Aug 25, 2012 · I have a numpy master array. Parameters: aarray_like Input data. This feature allows us to retrieve, modify and manipulate data at specific positions or ranges helps in making it easier to work with large datasets. index () method is the simplest way to find the index of an element in an array. searchsorted # numpy. Conclusion 123 Have you thought about using Python list's . array([1,2,3,4,5,1,6,1]) print np. element and test_elements are converted to arrays if they are not Apr 22, 2021 · Assuming I want to use the position of an element in a 2d list knowing the element itself, what would be the command to find the index? For a simple list the method list. ndim) where N is the number of non-zero items. Here's how to use these functions to find the maximum and minimum element's position in a Python list. Apr 12, 2023 · Boolean lists are often used by developers to check for True values during hashing. searchsorted(a, v, side='left', sorter=None) [source] # Find indices where elements should be inserted to maintain order. The index of the first element will be 0 and the last element will be indexed n-1, where n is the total number of elements. Indices are grouped by element. How to find the index of element in numpy array? You can use the numpy’s where () function to get the index of an element inside the array. Is there a way to specify what comparison operator to use? May 17, 2023 · Method #2 : Using numpy module This approach applies the same method but using numpy module. I want to know the indexes of the elements in A equal to a value and which indexes satisfy some condition: import numpy as np A = np. Feb 12, 2024 · This Python code utilizes the numpy library to find the index of the minimum element in a given list lst. stopCount and index < len (timeStamps): index += 1 Can this be Nov 8, 2024 · Introduction In Python's NumPy library, the argwhere() function is essential for locating indices of non-zero elements in an array. dtypedtype, optional Data type of the result. where () This function returns the indices of elements in an input array where the given condition is satisfied. A relatively short code can do this: index = 0 while time_points[index] <= 3: index += 1 index -= 1 Jun 26, 2018 · I'm trying to get the index values out of a numpy array, I've tried using intersects instead to no avail. array(a)>4]#X needs to be np. Find the indices into a sorted array a such that, if the corresponding elements in v were inserted before the indices, the order of a would be preserved. strings. g. Aug 29, 2020 · The elements of a NumPy array are indexed just like normal arrays. array as well Explanation: np. In this article, we will discuss different ways to find the index of the minimum element in a list in python. The following example illustrates the usage. We can use numpy's boolean indexing to create a boolean array of True for odd elements and False for even elements. nonzero() to get a tuple of arrays, one for each dimension of x containing the indices where the condition is True. Sep 3, 2019 · I'm trying find the index of the first element bigger than a threshold, like this: index = 0 while timeStamps [index] < self. where () in Python ? NumPy or Numerical Python which is a general purpose array processing package and it is used for working with arrays. Aug 22, 2014 · I have a NumPy array, A. array ( [ [1,1,0], [1,1,0], [0,0,1], [0,0,0]]) I want to find the indices of the first index (for every column) where the value is non-zero. Dec 30, 2024 · In this tutorial, I will explain how to find the closest value in an array using Python. argmin(lst) to find the index of the minimum element in the list using the NumPy function argmin(). x_indices, y_indices = np. closest_value = your_array [closest_index] By following these steps, you can easily find the index in a NumPy array that is closest to a specific target value. Since the sorted position is not necessary index k or k-1, we cannot guarantee that your_array[:k] contains the k smallest elements after numpy. One common task when dealing with numerical data is finding the closest value in an array to a given point. You can now use this value or index as needed for further calculations or analysis. It allows us to extract subsets of rows or columns efficiently. Notice however that your current solution leads to x_y_coord = [(0, 2), (1, 1)] that does NOT match @eumiro answer, and is wrong. We have explored different methods, including using the built-in index() method, loops, and the numpy library for numerical data. where(c Oct 1, 2020 · 2. It is ideal for extracting rows, columns or subsets from the nested list but less efficient for single element access. I am pretty known with np. You learned how to do this using the Python enumerate() function using both for loops and list comprehensions. Jan 19, 2012 · 41 I found this post: Python: finding an element in an array and it's about returning the index of an array through matching the values. array([10,1,2,5,6,2,3,8]) How could I extract an array containing the indices of the elements smaller than 6 so I get the Returns: isinndarray, bool Has the same shape as element. zeros(len(x)) for i in range(len(x)): positionx = np. In this example the element is 2. Example: The following code shows how to access an element of a NumPy array. Mar 18, 2022 · Conclusion In this tutorial, you learned how to find the index positions of all occurrences of an element in a Python list. Feb 2, 2024 · Use the max() and enumerate() Functions to Find the Index of the Maximum Element in a List in Python In Python, the enumerate variable attaches a counter variable to every element of the iterable. Jul 26, 2025 · Array indexing in NumPy refers to the method of accessing specific elements or subsets of data within an array. index(value) method? It return the index in the list of where the first instance of the value passed in is found. argwhere(a) [source] # Find the indices of array elements that are non-zero, grouped by element. where (condition [, x, y]) This problem can be solved efficiently using the numpy_indexed library (disclaimer: I am its author); which was created to address problems of this type. Let's discuss some ways to do the task. Jul 23, 2025 · In this article, we are going to find the index of the elements present in a Numpy array. Since we only need the first Even if it's a late answer: I think this is still a very good question and IMHO Python (without additional libraries or toolkits like numpy) is still lacking a convenient method to access the indices of list elements according to a manually defined filter. Because your data structure is , an easy way of sampling the value at the first index in every row is just by transposing the matrix and sampling the first list. Using Slicing Slicing is a powerful technique in Python for accessing a range of elements from nested lists. index(needle) inside a try block. The loop iterates through each index in the list. where() function is a versatile tool in the Python numpy library, primarily used to locate elements or indices in an array that meet certain conditions. >>> import numpy as np >>> arr = np. Note: If the element is not found, Python raises a ValueError. The sum () function calculates their total sum efficiently. This approach utilizes a min-heap data structure to find the N largest elements in a more memory-efficient way, especially when N is much smaller than the size of the array. Apr 2, 2010 · How do I find the nearest value in a numpy array? Example: np. find(array) # 0. bytes_ or np. Or sublist. In this article, we’ll see the different ways to index and slice NumPy arrays which helps us to work with our data more effectively Dec 27, 2016 · if element != 0: return list. indices(dimensions, dtype=<class 'int'>, sparse=False) [source] # Return an array representing the indices of a grid. What you are looking for is the argmax function which will give you the index of the Note NumPy slicing creates a view instead of a copy as in the case of built-in Python sequences such as string, tuple and list. Numpy provides many functions to compute indices of all null elements. View the answers with numpy integration, numpy arrays are far more efficient than Python lists. It works by searching through the list from the beginning and returning the index (position) of the first occurrence of the element you're looking for. Selecting a single element from a NumPy array Each element of these ndarrays can be accessed using its index number. Compute an array where the subarrays contain index values 0, 1, … varying only along the corresponding axis. Parameters: aarray_like, with StringDType, bytes_ or str_ dtype subarray_like, with np. nonzero, we identify the indices where the condition ( arr > 3) holds true and then extract the corresponding elements from the original array. Navigating arrays and matrices to find the index of the maximum value in an array is a routine task in data analysis, machine learning preprocessing, and general programming, where decisions based on the highest scores Feb 25, 2025 · In this article, I explained how to find the index of the maximum value in a list using Python. One is 2D and I'm selecting a column, an I need to figure out how I can find all the index of a value in a 2d numpy array. In this article, we see multiple ways to get the index of the first occurrence of a specified item Nov 11, 2021 · Learn how to use Python to get the index of the max item in a list, including when duplicates exist, using for loops, enumerate, and numpy. May 29, 2023 · An array is a data structure that is used to store elements of the same data type in order. where with only a condition, this is the same as calling np. I want to find all numpy array indices for Dec 5, 2012 · The simplest in my eyes would be to use numpy X[np. This array will have shape (N, a. I'm trying to find the index of every element of y in x. For example, in this case we could use numpy. Apr 22, 2025 · Finding the index of an element in a list is a common task in Python programming. nonzero() which returns you the indices of the non-zero elements of prediction==prediction. The highest value in x[0] is therefore x[0, 1, 2]. find # strings. This tutorial shows you how to find the index of an element in a list using the index() method and in operator in Python. nonzero(x > 0. Dec 5, 2024 · Finding Elements in a List with Python: Top 9 Methods In the realm of Python programming, efficiently locating elements within a list is a common task, especially when dealing with duplicates or requiring specific comparison logic. # Find the index of elements that meet a condition using a for loop This is a four-step process: Declare a new variable that stores an empty list. indices can be viewed as an n-dimensional generalisation of list. index (element) works, for e Aug 25, 2015 · For my use case, it's pretty fast, since it relies on parts of Python that are fast (list comprehensions, . 16. searchsorted (): Nov 8, 2024 · Introduction The numpy. where, eg. You can access an array element by referring to its index number. list comprehension vs. argmax () numpy. Given another array of search values, with repeating elements, I want to produce the indices of these search values in the master array. Additional Resources To learn more about related topics I have a list like this: myList = [0. where() Apr 29, 2021 · I would like to find the index of the last element that is lower or equal to three. Aug 27, 2021 · Find index of an array element in an array in numpy [duplicate] Asked 3 years, 7 months ago Modified 3 years, 7 months ago Viewed 109 times. However, we can use the List data structure or Numpy module to work with arrays. nan function. asarray(condition). Learn how to find the index of value in Numpy array using the numpy. where to find the indices of a single value, which is not faster than a list-comprehension, if the time to convert a list to an array is included The overhead of importing numpy and converting a list to a numpy. Jun 22, 2025 · NumPy is a fundamental library in the Python ecosystem, especially for scientific computing. The first element is technically the 0th element due to 0-based indexing. e Dec 31, 2024 · In this tutorial, I explained how to find the index of the maximum value in an array using Python, and there are multiple ways to accomplish it. Hence, you should Jan 1, 2025 · Learn how to find the index of an element in a Python array (or list) using methods like `index ()`, loops, and NumPy's `where ()`. where (arr != None) [0]. The where () function returns a tuple containing the indices where the specified condition is true. Method #1 : Using enumerate () and list comprehension enumerate () can do the task of hashing index with its value and couple with list Jul 23, 2025 · It extracts the element at index [1] from each sublist. So I would like a python code that gives me that 5. Oct 23, 2013 · 25 I need to find the index of more than one minimum values that occur in an array. what should I do about this? Apr 26, 2017 · I have a 1D array in numpy and I want to find the position of the index where a value exceeds the value in numpy array. where () function returns the indices of elements in an array that satisfy a given condition. For example, I have the following 2d array: ( [ [1 1 0 0], [0 0 1 1], [0 0 0 0]]) I need to find the index of a Dec 11, 2015 · This puts the element at index k (possibly unsorted) in sorted position. Use a for loop to iterate over the original list with enumerate(). lst = [array]; lst. 0) It works in this example Oct 12, 2016 · If this is not possible with some numpy routine, what is a fast way to do it in python? It would also be useful to me to be referred to some good numpy tutorials since I am a numpy beginner. array converts a to an array. Further, we now use nanargmax () function to search NumPy arrays and find the maximum value from the array elements without letting the NAN element affecting the search. Check if a condition Mar 1, 2024 · While NumPy is incredibly efficient, for very large arrays and where computational efficiency is paramount, the Python built-in module heapq can be used. Print the first k values of the sorted array. index (), sets, numpy indexing). where () method returns the indices of the elements that meet the condition. str_ dtype The substring to search for. array([item in b for item in a]) if a and b are 1-D sequences. for this, I used np. Method #1: Using np. 0, 2. indices # numpy. You must now provide two indices, one for each axis (dimension), to uniquely specify an element in this 2D array; the first number specifies an index along axis-0, the second specifies an index along axis-1. In this article, we will explore different approaches to solve this problem using Python and the NumPy library with examples. The function returns the index of the first occurrence that it finds starting from index 0 regardless of how many times it occurs within the list. Apr 27, 2025 · index () method in Python is a helpful tool when you want to find the position of a specific item in a list. argwhere # numpy. One common operation when working with NumPy arrays is to find the index of a specific value. However, for working with nested lists like this, one might often find it useful to use numpy. where() returns the indices of elements that meet the condition. find(needle) and avoid the extra iteration. Jun 1, 2017 · One can also use np. Aug 28, 2024 · Learn how to find the index of an element in a Python list using the index() method and other techniques. This includes finding the maximum element in an array or along a given axis of an array, as well as comparing two arrays to find the larger element in each index position. , rows or columns), in a NumPy array (ndarray) using various indexing. Sep 25, 2021 · I need to find the first location of zero in this array. For example, a = [0, 3, 0, 5, 8, 0, 2] we need to return all indexes of non-zero elements so that output should be [1, 3, 4, 6]. When you call np. In this case, the condition is test_list == np. Jul 23, 2021 · The predictions array here is two dimensional. Oct 20, 2023 · Retrieve the actual value from the array that corresponds to the index of the closest value. In this tutorial, we have studied about how to find the index of the last element in a NumPy array in Python. argmax() function for efficient computation. There are different kinds of indexing available depending on obj: basic indexing, advanced indexing and field access. It is 26% faster than the accepted answer, test2() below. Mar 27, 2024 · To find the index of the maximum element in a Python list, you can use the index method along with the max function. The boolean list is also used in certain dynamic programming paradigms in dynamic programming. array () function. 01) # (array([0, 0, 0, 0, 1, 1, 1, 1], dtype=int64), array([21, 23, 34, 49, 17, 24, 35, 40], dtype=int64)) A nice thing about it is that it can be used to index an array right away. if val == x checks for matching elements. If a match is found the index is added to indices. Step-by-step examples included numpy. For example, if we want to filter the Sep 26, 2020 · 30 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 less 9 seconds). index. Discover detailed examples and handle errors efficiently. dkpj voeog brnic fglph eldclhm yyqy hpmh rge ege ccubr