Dictionarys in python programming language.ppt

Dictionarys in python programming language.ppt

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  By: Vinay Agrawal
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  Dictionary  Dictionary isMutable.  Elements are arranged in the form of key-value pairs.  The symbol used to represent Dictionary is {} eg. d=:{‘Aman’:6.7, ’Raj’:9.5, ’Madhav’:8.6} key value  Key and its value is separated by a colon :
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   Keys mustbe immutable (may be string, tuple, number).  Values may be immutable or mutable.  General syntax of dictionary is as follows:- d={key1:value1,key2:value2,…….keyn:valuen}  Elements are ordered (After 3.7 Version)  It does not have the concept of numeric indexing, but it has the concept of key indexing. eg. print(d[key])
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  Q1. How wecan create empty dictionary? Ans. d={} OR d=dict()
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  Accessing Values d={‘Aryan’:8.5, ’Madhav’:9.5,’Dev’:6.5} print(d[‘Aryan’]) print(d.get(‘Dev’)) print(d[‘madhav’]) O/P: 8.5 6.5 Error
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  Dictionary is Mutable Addingelements in Dictionary  d[key]=value  d1.update(d2)- Adds the elements of d2 to the elements of d1. d1={‘Aman’:6.2, ‘Ajay’:8.2} d2={‘Madhav’:5.5, ‘Manav’:6.6} d1.update(d2)
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  Deleting elements fromdictionary  d.pop(key [, defaultvalue]) :- In this, it will delete the key-value pair based on provided key. 2nd parameter is optional, If it is there, it will return if key does not exist.  d.popitem() :- It removes the item that was last inserted into the dictionary. In versions before 3.7,it removes a random item. The removed item is the return value in the form of tuple.
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   d.clear() :-It will empties the dictionary.  del d[key] :-It will delete the key-value pair based on key.
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  Modifying the valueof dictionary  d[key]=value
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  Methods of Dictionary d.copy()  d.get(key[,value]): To access value of dictionary.  d.keys():- It will give list of all keys present in dictionary.  d.values():-It will give list of all values present in dictionary.  d.items():- It will give list of all keys,values present in dictionary. Return List of tuples.  d.has_key(key):-It works in Python 2.x version. Use in operator in Python 3.x
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   d.fromkeys(seq[,value]):- Thiswill help in creating a dictionary  d.setdefault(key,value)  len(d)  sorted(x):- x may be d.keys() or d.values()  zip(l1,l2) :  dict()
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  Looping over aDictionary d={‘amit’:6.5, ‘raj’:9.1,’madhav’:7.8} for i in d: print(i) for i in d: print(i,’ ‘,d[i]) for i, j in d.items(): print(i,’ ‘,j) for i in d.items(): print(i)
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  Dictionary Comprehension  d={i:i*ifor i in range(10)}  D={x:2*x for x in range(1,5)}
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  Programs 1.WAP that createsa dictionary of radius of a circle and its circumference. Expected O/P: Enter -1 to exit Enter radius:5 Enter radius:7 Enter radius:8 Enter radius:-1 {5:31.4, 8:50.24,7:43.96}
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  2.WAP that printsthe histogram of frequencies of characters occurring in a message. Expected O/P: Hello Hi H ** e * l ** o * * i *
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  3. WAP toinvert the dictionary( i.e keys becomes values and vice-versa) 4.WAP that has dictionary of names of students and a list of their marks in 4 subjects. Create another dictionary from this dictionary that has name of the students and their total marks. Find out the topper and his/her score.
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  5. Write aProgram to store a sparse matrix as a dictionary. Assume Sparse Matrix 0 1 2 3 4 0 0 0 0 1 0 1 2 0 0 0 3 2 0 0 0 4 0 Expected O/P: Sparse Matrix represented as dictionary: {(0,3):1, (2,3):4, (1,0):2, (1,4):3}
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  6. WAP thatprompts the user to enter a message. Now count and print the number of occurrences of each character. 7. WAP that creates a dictionary of cubes of odd numbers in the range 1-10. 8. WAP that enter string and then find the frequency of each word and represent in the form of dictionary.
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  Nested Dictionary OrangeCap Example (FindTop-Scorer along with score) D={ 'match1':{ ‘Virat':57, ‘Dhoni’:38 }, 'match2':{ ‘Maxwell':9, ‘Virat':42 }, 'match3':{ ‘Dhoni':41, ‘Taylor':63, ‘Maxwell’:91 } }
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  Solution D={ 'match1':{ 'Virat':57,'Dhoni':38 }, 'match2':{ 'Maxwell':9, 'Virat':42 }, 'match3':{ 'Dhoni':41, 'Taylor':63, 'Maxwell':91 } } x=D.values() D1={} print(x) for i in x: for j in i: if j in D1: D1[j]=D1[j]+i[j] else: D1[j]=i[j] print(D1) k=max(D1,key=D1.get) print("Player Name is ",k) print("Score is ",D1[k])
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  Some More Programs….. 1.WAP that has a dictionary of words in English Language and their corresponding words in Hindi. Define another Dictionary that has a list of words in Hindi and their corresponding words in Urdu. Take all words from English Language and display their meaning in both the languages. d1={‘Teacher’:’Shikshak’, ‘Book’:’Pustak’,’Friend’:’Mitr’} d2={‘Shikshak’:’Adhyapak’,’Pustak’:’Kitab’,’Mitr’:’Dost’} Expected O/P: Teacher in Hindi means Shikshak and in Urdu means Adhaypak Book in Hindi means Pustak and in Urdu means Kitab Friend in Hindi means Mitr and in Urdu means Dost
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  2. WAP thatcreates two dictionaries. One that stores conversion values from meters(1-5) to centimeters and other that stores values from centimeters to meters. Expected O/P: Meters to Centimeters {1:100,2:200,3:300,4:400,5:500} Centimeters to Meters {100:1,200:2,300:3,400:4,500:5}
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  3.WAP that hasa dictionary of states and their codes. Add another state in the pre-defined dictionary, print all the items in the dictionary and try to print code for a state that does not exist. Use setdefault() method states={‘Rajasthan’:101,’Haryana’:102} Expected O/P: {‘Rajasthan’:101,’Haryana’:102,’Assam’:103} None {‘Rajasthan’:101,’Haryana’:102,’Assam’:103,’Goa’:104}