Python Articles - Page 875 of 1048

You can update a dictionary by adding a new entry or a key-value pair, modifying an existing entry, or deleting an existing entry as shown below in the simple example −Example Live Demo#!/usr/bin/python dict = {'Name': 'Zara', 'Age': 7, 'Class': 'First'} dict['Age'] = 8; # update existing entry dict['School'] = "DPS School"; # Add new entry print "dict['Age']: ", dict['Age'] print "dict['School']: ", dict['School']OutputWhen the above code is executed, it produces the following result −dict['Age']: 8 dict['School']: DPS School

Accessing Values of Dictionary in Python Accessing dictionary items in Python involves retrieving the values associated with specific keys within a dictionary data structure. Dictionaries are composed of key-value pairs, where each key is unique and maps to a corresponding value. Accessing dictionary items allows us to retrieve these values by providing the respective keys. There are various ways to access dictionary items in Python. They include − Using square brackets[] The get() method Using keys() Method Using values() Method ... Read More

Python includes the following tuple functions −Sr.NoFunction with Description1cmp(tuple1, tuple2)Compares elements of both tuples.2len(tuple)Gives the total length of the tuple.3max(tuple)Returns item from the tuple with max value.4min(tuple)Returns item from the tuple with min value.5tuple(seq)Converts a list into tuple.

Any set of multiple objects, comma-separated, written without identifying symbols, i.e., brackets for lists, parentheses for tuples, etc., default to tuples, as indicated in these short examples −Example Live Demo#!/usr/bin/python print 'abc', -4.24e93, 18+6.6j, 'xyz'; x, y = 1, 2; print "Value of x , y : ", x,y;OutputWhen the above code is executed, it produces the following result −abc -4.24e+93 (18+6.6j) xyz Value of x , y : 1 2

Tuples respond to the + and * operators much like strings; they mean concatenation and repetition here too, except that the result is a new tuple, not a string.In fact, tuples respond to all of the general sequence operations we used on strings in the prior chapter −Python ExpressionResultsDescriptionlen((1, 2, 3))3Length(1, 2, 3) + (4, 5, 6)(1, 2, 3, 4, 5, 6)Concatenation('Hi!',) * 4('Hi!', 'Hi!', 'Hi!', 'Hi!')Repetition3 in (1, 2, 3)TrueMembershipfor x in (1, 2, 3): print x,1 2 3Iteration

Removing individual tuple elements is not possible. There is, of course, nothing wrong with putting together another tuple with the undesired elements discarded.To explicitly remove an entire tuple, just use the del statement.Example Live Demo#!/usr/bin/python tup = ('physics', 'chemistry', 1997, 2000); print tup; del tup; print "After deleting tup : "; print tup;OutputThis produces the following result. Note an exception raised, this is because after del tup tuple does not exist any more −('physics', 'chemistry', 1997, 2000) After deleting tup : Traceback (most recent call last): File "test.py", line 9, in print tup; NameError: name 'tup' is not defined

Python includes the following list functions −Sr.NoFunction with Description1cmp(list1, list2)Compares elements of both lists.2len(list)Gives the total length of the list.p>3max(list)Returns item from the list with max value.4min(list)Returns item from the list with min value.5list(seq)Converts a tuple into list.Python includes following list methodsSr.NoMethods with Description1list.append(obj)Appends object obj to list2list.count(obj)Returns count of how many times obj occurs in list3list.extend(seq)Appends the contents of seq to list4list.index(obj)Returns the lowest index in list that obj appears5list.insert(index, obj)Inserts object obj into list at offset index6list.pop(obj=list[-1])Removes and returns last object or obj from list7list.remove(obj)Removes object obj from list8list.reverse()Reverses objects of list in place9list.sort([func])Sorts objects of list, use ... Read More

Lists respond to the + and * operators much like strings; they mean concatenation and repetition here too, except that the result is a new list, not a string.In fact, lists respond to all of the general sequence operations we used on strings in the prior chapter.Python ExpressionResultsDescriptionlen([1, 2, 3])3Length[1, 2, 3] + [4, 5, 6][1, 2, 3, 4, 5, 6]Concatenation['Hi!'] * 4['Hi!', 'Hi!', 'Hi!', 'Hi!']Repetition3 in [1, 2, 3]TrueMembershipfor x in [1, 2, 3]: print x,1 2 3Iteration

To remove a list element, you can use either the del statement if you know exactly which element(s) you are deleting or the remove() method if you do not know.Example Live Demo#!/usr/bin/python list1 = ['physics', 'chemistry', 1997, 2000]; print list1 del list1[2]; print "After deleting value at index 2 : " print list1OutputWhen the above code is executed, it produces the following result −['physics', 'chemistry', 1997, 2000] After deleting value at index 2 : ['physics', 'chemistry', 2000]Note − remove() method is discussed in subsequent section.

In Python, lists are one of the built-in data structures that are used to store collections of data. The lists are mutable, which means we can modify its element after it is created. You can update single or multiple list elements using append, insert, extend, remove, and clear to change the list content by adding, updating, or removing elements from the list object. In this article, we will discuss how we can update an existing element in the list. The list is an index-based sequential data structure so that we can access the list elements by their index position, ... Read More