To join specific list elements (e.g., with indices 0, 2, and 4) and return the joined string that’s the concatenation of all those, use the expression ”.join([lst[i] for i in [0, 2, 4]]). The list comprehension statement creates a list consisting of elements lst[0], lst[2], and lst[4]. The ”.join() method concatenates those elements using the … Read more
Given a list of strings. Join the first with the second string, the second with the third, and so on. The one-liner [lst[i] + lst[i+1] for i in range(0, len(lst), 2)] solves the problem by using the range function to iterate over every other index i=0, 2, 4, 5, … to concatenate the i-th and … Read more
The most Pythonic way to merge multiple lists l0, l1, …, ln into a list of tuples (grouping together the i-th elements) is to use the zip() function zip(l0, l1, …, ln). If you store your lists in a list of lists lst, write zip(*lst) to unpack all inner lists into the zip function. The … Read more
If the search phrase “Python Join List Range” brought you here, you’re having most likely one of the following problems: You don’t know how to concatenate two range() iterables, or You want to use .join() to create a string from a range() iterable—but it doesn’t work. In any case, by reading this article, I hope … Read more
The most efficient method to join a list of Python strings in reverse order is to use the Python code ”.join(l[::-1]). First, reverse the list l using slicing with a negative step size l[::-1]. Second, glue together the strings in the list using the join(…) method on the empty string ”. Problem: Given a list … Read more
Problem: Say, you’ve got a list of dictionaries: Notice how the first and the last dictionaries carry the same key ‘a’. How do you merge all those dictionaries into a single dictionary to obtain the following one? Notice how the value of the duplicate key ‘a’ is the value of the last and not the … Read more
When teaching the Finxter Python students, I’m often shocked how even intermediate-level coders do not understand the very basic foundations of computer science. In CS, there’s almost nothing as fundamental as a simple, plain byte. (You know, that sequence of 0s and 1s called bits). This tutorial aims to clarify some misconceptions and questions regarding … Read more
To intersect multiple sets, stored in a list l, use the Python one-liner l.pop().intersection(*l) that takes the first set from the list, calls the intersection() method on it, and passes the remaining sets as arguments by unpacking them from the list. A set is a unique collection of unordered elements. The intersection operation creates a … Read more
The most efficient way to join multiple sets (stored in a list of sets), use the Python one-liner set().union(*list) that creates a new set object, calls the union() method on the new object, and unpacks all sets from the list of sets into the union() method’s argument list. A set is a unique collection of … Read more
The most Pythonic way to convert a list of tuples to a string is to use the built-in method str(…). If you want to customize the delimiter string, the most Pythonic way is to concatenate the join() method and the map() function ‘\n’.join(map(str, lst)) to convert all tuples to strings and gluing those together with … Read more
Problem: Given a list of Boolean elements. What’s the best way to join all elements using the logical “OR” and logical “AND” operations? Example: Convert the list [True, True, False] using The logical “AND” operation to True and True and False = False, The logical “OR” operation to True or True or False = True, … Read more
The ‘_’.join(list) method on the underscore string ‘_’ glues together all strings in the list using the underscore string as a delimiter—and returns a new string. For example, the expression ‘_’.join([‘a’, ‘b’, ‘c’]) returns the new string ‘a_b_c’. Definition and Usage The string.join(iterable) method joins the string elements in the iterable to a new string … Read more