Chapter 1 Review Of Python Basics - WordPress

String FunctionsString.capitalize()Converts first character to Capital LetterString.find()Returns the Lowest Index of SubstringString.index()Returns Index of SubstringString.isalnum()Checks Alphanumeric CharacterString.isalpha()Checks if All Characters are AlphabetsString.isdigit()Checks Digit CharactersString.islower()Checks if all Alphabets in a String.are LowercaseString.isupper()returns if all characters are uppercase charactersString.join()Returns a Concatenated StringString.lower()returns lowercased stringString.upper()returns uppercased stringlen()Returns Length of an Objectord()returns Unicode code point for Unicode characterreversed()returns reversed iterator of a sequenceslice()creates a slice object specified by range()Neha Tyagi, KV 5 Jaipur II Shift

List Creation List is a standard data type of Python. It is a sequence whichcan store values of any kind. List is represented by square brackets “ [ ] “For ex []Empty list [1, 2, 3]integers list [1, 2.5, 5.6, 9]numbers list (integer and float) [ ‘a’, ‘b’, ‘c’]characters list [‘a’, 1, ‘b’, 3.5, ‘zero’] mixed values list [‘one’, ’two’, ’three’] string list In Python, only list and dictionary are mutable data types, restof all the data types are immutable data types.Neha Tyagi, KV 5 Jaipur II Shift

List Creation List can be created in following ways Empty list L [] list can also be created with the following statementL list( ) Long listseven [0, 2, 4, 6, 8, 10 ,12 ,14 ,16 ,18 ,20 ] Nested list L [ 3, 4, [ 5, 6 ], 7]Another methodNeha Tyagi, KV 5 Jaipur II ShiftThis is a Tuple

List Creation-As we have seen in the exampleThat when we have suppliedvalues as numbers to a list even thenThey have automatically converted to string– If we want to pass values to a list in numeric form then we have to writefollowing function eval(input())L eval(input(“Enter list to be added “))eval ( ) function identifies type of the passed string and then return it.Another exampleString ValuesNeha Tyagi, KV 5 Jaipur II Shift

Accessing a ListFirst we will see the similarities between a List and a String.List is a sequence like a string.List also has index of each of its element.Like string, list also has 2 index, one for forward indexing (from0, 1, 2, 3, .to n-1) and one for backward indexing(from -n to 1). In a list, values can be accessed like string. Forward index 0 1 2 3 4 5List R ESP O NBackward index -14 -13 -12 -11 -10 -9678910 11 12 13SIBILITY-8-7-6-5-4-3-2-1Neha Tyagi, KV 5 Jaipur II Shift

Accessing a List len( ) function is used to get the length of a list.Important 1:membershipoperator (in, not in) worksin list similarly as they workin other sequence. L[ i ] will return the values exists at i index. L [ i : j ] will return a new list with the values from i index to j index excludingj index.Important 2: operatoradds a list at the end ofother list whereas *operator repeats a list.Neha Tyagi, KV 5 Jaipur II Shift

Difference between a List and a String Main difference between a List and a string is that string isimmutable whereas list is mutable. Individual values in string can’t be change whereas it ispossible with list.Value didn’tchange in string.Error shown.Value got changedin list specifyinglist is mutableNeha Tyagi, KV 5 Jaipur II Shift

Traversal of a list Traversal of a list means to access and process each andevery element of that list. Traversal of a list is very simple with for loop –for item in list :*Python supports UNICODE thereforeoutput in Hindi is also possibleNeha Tyagi, KV 5 Jaipur II Shift

List Operations ( , *) Main operations that can be performed on lists are joining list,replicating list and list slicing. To join Lists, operator , is used which joins a list at the end ofother list. With operator, both the operands should be of listtype otherwise error will be generated. To replicate a list, * operator , is used.Neha Tyagi, KV 5 Jaipur II Shift

List Operations (Slicing) To slice a List, syntax isseq list [ start : stop ] Another syntax for List slicing is –seq list[start:stop:step]Neha Tyagi, KV 5 Jaipur II Shift

Use of slicing for list Modification Look carefully at following examples-New value is being assigned here.Here also, new value is being assigned.See the difference between both the results.144 is a value and not a sequence.Neha Tyagi, KV 5 Jaipur II Shift

List Functions and Methods– Python provides some built-in functions for list manipulation– Syntax is like list-object . method-name FunctionDetailsList.index( item )Returns the index of passed items.List.append( item )Adds the passed item at the end of list.List.extend( list )Append the list (passed in the form of argument) at the end of listwith which function is called.List.insert( pos , item )Insert the passed element at the passed position.List.pop( index )Delete and return the element of passed index. Index passing isoptional, if not passed, element from last will be deleted.List.remove( value )It will delete the first occurrence of passed value but does notreturn the deleted value.Neha Tyagi, KV 5 Jaipur II Shift

List Functions and MethodsFunctionDetailsList.clear ( )It will delete all values of list and gives an empty list.List.count ( item )It will count and return number of occurrences of the passed element.List.reverse ( )It will reverse the list and it does not create a new list.List.sort ( )It will sort the list in ascending order. To sort the list in descendingorder, we need to write----- list.sort(reverse True).Neha Tyagi, KV 5 Jaipur II Shift

Creation of Tuple In Python, “( )” parenthesis are used for tuple creation.()empty tuple( 1, 2, 3)integers tuple( 1, 2.5, 3.7, 7)numbers tuple(‘a’, ’b’, ’c’ )characters tuple( ‘a’, 1, ‘b’, 3.5, ‘zero’)mixed values tuple(‘one’, ’two’, ’three’, ’four’)string tuple*Tuple is an immutable sequence whose values can not be changed.Neha Tyagi, KV 5 Jaipur II Shift

Creation of TupleLook at following examples of tuple creation carefully Empty tuple: Single element tuple: Long tuple: Nested tuple:Neha Tyagi, KV 5 Jaipur II Shift

Creation of Tupletuple() function is used to create a tuple from other sequences.See examplesTuple creation from stringTuple creation from listTuple creation from inputAll these elements are ofcharacter type. To havethese in different types,need to write followingstatement.Tuple eval(input(“Enterelements”))Neha Tyagi, KV 5 Jaipur II Shift

Accessing a Tuple In Python, the process of tuple accessing is same aswith list. Like a list, we can access each and everyelement of a tuple. Similarity with List- like list, tuple also has index. Allfunctionality of a list and a tuple is same except mutability.Forward index 0Tuple RBackward index -1412345678910 11 12 13ESPONSIBILITY-13-12-11-10-9-8-7-6-5-4-3-2-1 len ( ) function is used to get the length of tuple.Neha Tyagi, KV 5 Jaipur II Shift

Accessing a Tuple Indexing and Slicing: T[ i ] T[ i : j ] T[i:j:n]returns the item present at index i.returns a new tuple having all the items of T fromindex i to j.returns a new tuple having difference of n elementsof T from index i to j.index i to j. Membership operator: Working of membership operator “in” and “not in” is same asin a list. (for details see the chapter- list manipulation). Concatenation and Replication operators: operator adds second tuple at the end of first tuple. * operator repeatselements of tuple.Neha Tyagi, KV 5 Jaipur II Shift

Accessing a Tuple Accessing Individual elements- Traversal of a Tuple –for item in tuple :#to process every element.OUTPUTNeha Tyagi, KV 5 Jaipur II Shift

Tuple Operations Tuple joining Both the tuples should be there to addwith . Some errors in tuple joining In Tuple numberIn Tuple complex numberIn Tuple stringIn Tuple listTuple (5) will also generate error because when adding a tuple witha single value, tuple will also be considered as a value and not atuple. Tuple Replication-Neha Tyagi, KV 5 Jaipur II Shift

Tuple SlicingTuple will show till last element of list irrespective of upperlimit.Every alternate element will be shown.Every third element will be shown.Neha Tyagi, KV 5 Jaipur II Shift

Dictionary Creation To create a dictionary, it is needed to collect pairs ofkey:value in “{ }”. dictionary-name { key1 : value1 , key2 : value2 , key3 : value3 . . . }Example:teachers {“Rajeev”:”Math”, SB”:”CS”}In above given example :Key-value �“SB”:”CS”“SB”“CS”Neha Tyagi, KV 5 Jaipur II Shift

Dictionary Creation Some examples of Dictionary areDict1 { }# this is an empty dictionary without any element.DayofMonth { January”:31, ”February”:28, ”March”:31, ”April”:30, ”May”:31, ”June”:30,”July”:31, ”August”:31, ”September”:30, ”October”:31, ”November”:30,”December”:31}FurnitureCount { “Table”:10, “Chair”:13, “Desk”:16, “Stool”:15, “Rack”:15 }– By above examples you can easily understand about the keysand their values.– One thing to be taken care of is that keys should always be ofimmutable type.Note: Dictionary is also known as associative array or mappingor hashes .Neha Tyagi, KV 5 Jaipur II Shift

Dictionary Creation– Keys should always be of immutable type.– If you try to make keys as mutable, python shown error in it.For example-Here key is a list which isof mutable type.Here error shows that you are trying to create a keyof mutable type which is not permitted.Neha Tyagi, KV 5 Jaipur II Shift

Accessing a Dictionary To access a value from dictionary, we need to use keysimilarly as we use an index to access a value from a list. We get the key from the pair of Key: value.teachers {“Rajeev”:”Math”, SB”:”CS”} If we execute following statement from above example- We have selected key “Rajeev” and on printing it, Math gotprinted. Another exampleIf we access a non-key, error will come.Neha Tyagi, KV 5 Jaipur II Shift

Traversal of a Dictionary To traverse a Dictionary, we use for loop. Syntax isfor item in dictionary :Here, notable thing is that every key of each pair ofdictionary d is coming in k variable of loop. After thiswe can take output with the given format and withprint statement.Assignment : Develop a dictionary of your friends in which keywill be your friend’s name and his number will be its value.Neha Tyagi, KV 5 Jaipur II Shift

Traversal of Dictionary To access key and value we need to use keys() andvalues().for example- d.keys( ) function will display only key. d.values ( ) function will display value only.Neha Tyagi, KV 5 Jaipur II Shift

Features of Dictionary1. Unordered set: dictionary is a unordered collection of key:value pairs.2. Not a sequence: like list, string and tuple , it is not a sequence becauseit is a collection of unordered elements whereas a sequence is a collectionof indexed numbers to keep them in order.3. Keys are used for its indexing because according to Python key can be ofimmutable type. String and numbers are of immutable type and thereforecan be used as a key. Example of keys are as under-Key of a Dictionary should always be ofimmutable type like number, string or tuplewhereas value of a dictionary can be of any type.Neha Tyagi, KV 5 Jaipur II Shift

Features of Dictionary4. Keys should be unique : Because keys are used to identifyvalues so they should be unique.5. Values of two unique keys can be same.6. Dictionary is mutable hence we can change value of a certainkey. For this, syntax is dictionary [ key ] value 4. Internally it is stored as a mapping. Its key:value areconnected to each other via an internal function called hashfunction**. Such process of linking is knows as mapping.**Hash-function is an internal algorithm to link a and itsvalue.Neha Tyagi, KV 5 Jaipur II Shift

Working with Dictionary Here we will discuss about various operation of dictionary like elementadding, updation, deletion of an element etc. but first we will learn creationof a dictionary. Dictionary initialization- For this we keep collection of pairs ofkey:value separated by comma (,) and then place thiscollection inside “{ }”. Addition of key:value pair to an empty dictionary. There aretwo ways to create an empty dictionary1. Employee { }2. Employee dict( )After that use following syntax- dictionary [ key ] value Neha Tyagi, KV 5 Jaipur II Shift

Working with Dictionary3. Creation of a Dictionary with the pair of name andvalue: dict( ) constructor is used to create dictionarywith the pairs of key and value. There are variousmethods for thisI.By passing Key:value pair as an argument:The point to be noted is that here no inverted commas were placed inargument but they came automatically in dictionary.II. By specifying Comma-separated key:value pair-Neha Tyagi, KV 5 Jaipur II Shift

Working with DictionaryIII. By specifying Keys and values separately:For this, we use zip() function in dict ( ) constructor-IV. By giving Key:value pair in the form of separate sequence:By passing ListBy passing tuple of a listBy passing tuple of tupleNeha Tyagi, KV 5 Jaipur II Shift

Adding an element in Dictionaryfollowing syntax is used to add an element in Dictionary-Nesting in Dictionarylook at the following example carefully in which element of a dictionary isa dictionary itself.Neha Tyagi, KV 5 Jaipur II Shift

Updation in a Dictionaryfollowing syntax is used to update an element in Dictionary dictionary [ ExistingKey ] value WAP to create a dictionary containing names of employee as key and their salary asvalue.OutputNeha Tyagi, KV 5 Jaipur II Shift

Deletion of an element from a Dictionaryfollowing two syntaxes can be used to delete an element form aDictionary. For deletion, key should be there otherwise pythonwill give error.1. del dictionary [ key ]- it only deletes the value anddoes not return deleted value.Value did not return after deletion.2. dictionary .pop( key ) it returns the deleted valueafter deletion.Value returned after deletion.If key does not match, givenmessage will be printed.Neha Tyagi, KV 5 Jaipur II Shift

Detection of an element from a DictionaryMembership operator is used to detect presence of an elementin a Dictionary.1. key in dictionary it gives true on finding the key otherwise gives false.2. key not in dictionary it gives true on not finding the key otherwise gives false.False* in and not in does not applyon values, they can only workwith keys.Neha Tyagi, KV 5 Jaipur II Shift

Pretty Printing of a DictionaryTo print a Dictionary in a beautify manner, we need to importjson module. After that following syntax of dumps ( ) will be used.json.dumps( ,indent n )Neha Tyagi, KV 5 Jaipur II Shift

Program to create a dictionary by counting words in a lineHere a dictionary iscreated of wordsand their frequency.Neha Tyagi, KV 5 Jaipur II Shift

Dictionary Function and Method1. len( ) Method : it tells the length of dictionary.2. clear( ) Method : it empties the dictionary.3. get( ) Method : it returns value of the given key.It works similarly as dictionary [ key ]On non finding of a key, default message can begiven.Neha Tyagi, KV 5 Jaipur II Shift

Dictionary Function and Method4. items( ) Method : it returns all items of a dictionary in the formof tuple of (key:value).5. keys( ) Method : it returns list of dictionary keys.6. values( ) Method : it returns list of dictionary values.Neha Tyagi, KV 5 Jaipur II Shift

Dictionary Function and Method7. Update ( ) Method: This function merge the pair of key:valueof a dictionary into other dictionary. Change and addition inthis is possible as per need. Example-In the above given example, you can see that change is done inthe values of similar keys whereas dissimilar keys got joined withtheir values.Neha Tyagi, KV 5 Jaipur II Shift

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Python (a computer language) In last class we have learned about Python. In this class we will learn Python with some new techniques. We know that Python is a powerful and high level language and it is an interpreted language. Python gives us two modes of working- -Interactive mode -Script mode Neha Tyagi, KV 5 Jaipur II Shift