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Articles by Nizamuddin Siddiqui
Page 113 of 196
Python - Ways to create triplets from given list
A list is a collection which is ordered and changeable. In Python lists are written with square brackets. You access the list items by referring to the index number. Negative indexing means beginning from the end, -1 refers to the last item. You can specify a range of indexes by specifying where to start and where to end the range. When specifying a range, the return value will be a new list with the specified items.Example# triplets from list of words. # List of word initialization list_of_words = ['I', 'am', 'Vishesh', 'and', 'I', 'like', 'Python', 'programming'] # Using list comprehension List ...
Read MorePython - Ways to find indices of value in list
Usually, we require to find the index, in which the particular value is located. There are many method to achieve that, using index() etc. But sometimes require to find all the indices of a particular value in case it has multiple occurrences in list.Example# using filter() # initializing list test_list = [1, 3, 4, 3, 6, 7] # printing initial list print ("Original list : " + str(test_list)) # using filter() # to find indices for 3 res_list = list(filter(lambda x: test_list[x] == 3, range(len(test_list)))) # printing resultant list print ("New indices list : " + str(res_list)) # ...
Read MorePython - Ways to flatten a 2D list
A list is a collection which is ordered and changeable. In Python lists are written with square brackets. You access the list items by referring to the index number. Negative indexing means beginning from the end, -1 refers to the last item. You can specify a range of indexes by specifying where to start and where to end the range. When specifying a range, the return value will be a new list with the specified items.Example# using chain.from_iterables # import chain from itertools import chain ini_list = [[1, 2, 3], [3, 6, 7], [7, 5, 4]] # ...
Read MorePython - Ways to format elements of given list
A list is a collection which is ordered and changeable. In Python lists are written with square brackets. You access the list items by referring to the index number. Negative indexing means beginning from the end, -1 refers to the last item. You can specify a range of indexes by specifying where to start and where to end the range. When specifying a range, the return value will be a new list with the specified items.Example# List initialization Input = [100.7689454, 17.232999, 60.98867, 300.83748789] # Using list comprehension Output = ["%.2f" % elem for elem in Input] # Printing output ...
Read MorePython - Ways to invert mapping of dictionary
Dictionary is a collection which is unordered, changeable and indexed. In Python, dictionaries are written with curly brackets, and they have keys and values. It is widely used in day to day programming, web development, and machine learning.Example# using dict comprehension # initialising dictionary ini_dict = {101: "vishesh", 201 : "laptop"} # print initial dictionary print("initial dictionary : ", str(ini_dict)) # inverse mapping using dict comprehension inv_dict = {v: k for k, v in ini_dict.items()} # print final dictionary print("inverse mapped dictionary : ", str(inv_dict)) # using zip and dict functions # initialising dictionary ini_dict = {101: "vishesh", 201 : ...
Read MorePython - Which is faster to initialize lists?
Python is a very flexible language where a single task can be performed in a number of ways, for example initializing lists can be performed in many ways. However, there are subtle differences in these seemingly similar methods. Python which is popular for its simplicity and readability is equally infamous for being slow compared to C++ or Java. The ‘for’ loop is especially known to be slow whereas methods like map() and filter() known to be faster because they are written in C.Example# import time module to calculate times import time # initialise lists to save the times forLoopTime = ...
Read MoreHow to solve the simultaneous linear equations in R?
The data in simultaneous equations can be read as matrix and then we can solve those matrices to find the value of the variables. For example, if we have three equations as −x + y + z = 6 3x + 2y + 4z = 9 2x + 2y – 6z = 3then we will convert these equations into matrices and solve them using solve function in R.Example1> A AOutput [, 1] [, 2] [, 3] [1, ] 1 1 2 [2, ] 3 2 4 [3, ] 2 3 -6> b bOutput[, 1] ...
Read MoreHow to remove a character in an R data frame column?
To remove a character in an R data frame column, we can use gsub() function which will replace the character with blank. For example, if we have a data frame called df that contains a character column say x which has a character ID in each value then it can be removed by using the command gsub("ID", "", as.character(df$x)).Example1Consider the below data frame −> x1 x2 df1 df1Output x1 x2 1 Male1 8 2 Female1 4 3 Male1 9 4 Male1 2 5 Male1 7 6 Female1 5 7 Male1 3 8 ...
Read MoreHow to convert more than one column in R data frame to from integer to numeric in a single line code?
To convert columns of an R data frame from integer to numeric we can use lapply() function. For example, if we have a data frame df that contains all integer columns then we can use the code lapply(df,as.numeric) to convert all of the columns data type into numeric data type.Example1Consider the below data frame −set.seed(871) x1
Read MoreHow to find the R version you are using?
Most of the times, we need to use packages in R and some packages are restricted to different versions in R, generally to newer versions. Therefore, we might need to find which version of R we are using. To find the R version, we can directly use the command R.Version().ExampleR.version.stringOutput[1] "R version 4.0.2 (2020−06−22)"
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