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Technical articles with clear explanations and examples
Python – Substitute prefix part of List
When working with lists, you may need to substitute the prefix (beginning) part of one list with another list. Python provides a simple approach using list slicing with the : operator and the len() function. What is Prefix Substitution? Prefix substitution means replacing the first N elements of a list with elements from another list, where N is the length of the replacement list. Example Here's how to substitute the prefix part of a list ? # Define two lists original_list = [29, 77, 19, 44, 26, 18] replacement_list = [15, 44, 82] ...
Read MorePython - Merge DataFrames of different length
To merge DataFrames of different lengths, we use the merge() method with different join types. The left join keeps all rows from the left DataFrame and matches rows from the right DataFrame where possible. Creating DataFrames of Different Lengths Let's create two DataFrames with different lengths to demonstrate merging ? import pandas as pd # Create DataFrame1 with length 4 dataFrame1 = pd.DataFrame({ "Car": ['BMW', 'Lexus', 'Audi', 'Jaguar'], "Price": [50000, 45000, 48000, 60000] }) print("DataFrame1 ...", dataFrame1) print("DataFrame1 length =", len(dataFrame1)) DataFrame1 ... ...
Read MorePython – Cross mapping of Two dictionary value lists
When it is required to cross-map two dictionary valued lists, the setdefault and extend methods are used. This technique allows you to map values from one dictionary to another based on matching keys and indices. Understanding Cross Mapping Cross mapping involves using values from the first dictionary as keys to lookup corresponding values in the second dictionary. The result combines these lookups into a new dictionary structure. Example Below is a demonstration of cross mapping two dictionaries − my_dict_1 = {"Python" : [4, 7], "Fun" : [8, 6]} my_dict_2 = {6 : [5, 7], ...
Read MorePython – Check if elements index are equal for list elements
When it is required to check if the index of elements matches their values or compare elements at the same positions across lists, we can use simple iteration with the enumerate() function. Basic Example: Check if Index Equals Value Here's how to check if any element's index equals its value ? data = [0, 2, 1, 3, 5] print("The list is:") print(data) # Check if any element equals its index index_equals_value = [] for index, element in enumerate(data): if index == element: ...
Read MorePython – Convert List to Index and Value dictionary
When you need to convert a list into a dictionary containing separate index and value arrays, Python's enumerate() function provides an elegant solution. This approach creates a structured dictionary with index and values keys. Basic Example Here's how to convert a list to an index-value dictionary ? my_list = [32, 0, 11, 99, 223, 51, 67, 28, 12, 94, 89] print("The list is:") print(my_list) my_list.sort(reverse=True) print("The sorted list is:") print(my_list) index, value = "index", "values" my_result = {index : [], value : []} for id, vl in enumerate(my_list): my_result[index].append(id) ...
Read MorePython – Extend consecutive tuples
When working with tuples in Python, you may need to extend consecutive tuples by combining each tuple with the next one in the sequence. This creates a new list where each element is the concatenation of two adjacent tuples. Example Below is a demonstration of extending consecutive tuples ? my_list = [(13, 526, 73), (23, 67, 0, 72, 24, 13), (94, 42), (11, 62, 23, 12), (93, ), (83, 61)] print("The list is :") print(my_list) my_list.sort(reverse=True) print("The list after sorting in reverse is :") print(my_list) my_result = [] for index in range(len(my_list) - ...
Read MorePython – Filter unique valued tuples
When it is required to filter unique valued tuples from a list of tuples, the set() method can be used to remove duplicates. However, since the example doesn't contain actual duplicates, let's explore different scenarios and approaches. Basic Approach Using set() The most straightforward way to filter unique tuples is converting the list to a set and back to a list − my_list = [(42, 51), (46, 71), (14, 25), (26, 91), (56, 0), (11, 1), (99, 102)] print("The list of tuple is :") print(my_list) my_result = list(set(my_list)) print("The result after removing duplicates is :") ...
Read MorePython – 3D Matrix to Coordinate List
When working with 3D matrices in Python, you might need to convert them into coordinate pairs. This process uses list comprehension and the zip() function to pair corresponding elements from different sublists. Understanding 3D Matrix Structure A 3D matrix in Python is essentially a list containing multiple 2D matrices (lists of lists). Each 2D matrix contains rows of data that can be paired together ? # 3D matrix structure: [2D_matrix1, 2D_matrix2, 2D_matrix3] # Each 2D matrix: [[row1], [row2]] matrix_3d = [ [['He', 'Wi'], ['llo', 'll']], # First ...
Read MorePython – Cross Pairing in Tuple List
Cross pairing in a tuple list means matching tuples from two lists based on their first element and creating pairs with their second elements. This is achieved using zip(), list comprehension, and the == operator. What is Cross Pairing? Cross pairing compares tuples from two lists and creates new pairs when the first elements match. For example, if both lists contain tuples starting with "Hi", their second elements get paired together. Example Below is a demonstration of cross pairing in tuple lists − list_1 = [('Hi', 'Will'), ('Jack', 'Python'), ('Bill', 'Mills'), ('goodwill', 'Jill')] list_2 ...
Read MorePython – Sort grouped Pandas dataframe by group size?
To group Pandas data frame, we use groupby(). To sort grouped data frames in ascending or descending order, use sort_values(). The size() method is used to get the data frame size. Steps Involved The steps included in sorting the pandas data frame by its group size are as follows ? Importing the pandas library and creating a Pandas DataFrame. Grouping the columns by using the ...
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