DICTIONARY IN PYTHON

Dictionary is used to represent group of key, value pairs into a single entity. Insertion order is not preserved. Duplicate keys are not allowed but duplicate values can be there. Heterogeneous keys and values are allowed. Immutable objects only allowed for keys.

Example –

x={}
print x
print type(x)
y=dict([(1,'apple'),(2,'ball')])
print y
print type(y)
z={'java':90,'Python':99,'hadoop':95}
print z
print type(z)
print len(z)

Output –

{}

<type 'dict'>

{1: 'apple', 2: 'ball'}

<type 'dict'>

{'Python': 99, 'java': 90, 'hadoop': 95}

<type 'dict'>

3

Example –

x={10:'abc',20:'def',30:'xyz',20:'rakesh',40:'ghi'}
print x
print x[10]
print x[20]
print x[50]

Output –

Traceback (most recent call last):

{40: 'ghi', 10: 'abc', 20: 'rakesh', 30: 'xyz'}

abc

  File "C:/Users/om/PycharmProjects/Pythonn/if3.py", line 5, in <module>

rakesh

    print x[50]

KeyError: 50

Example –

x={10:12.12,True:100,1.1:'abc','def':False,'names':['hyd','bang','ghy'],

(1.1,2.2,3.3):'india'}
print x
k=x.keys()
print k
v=x.values()
print v

Output –

{True: 100, 1.1: 'abc', 10: 12.12, (1.1, 2.2, 3.3): 'india', 'names': ['hyd', 'bang', 'ghy'], 'def': False}

[True, 1.1, 10, (1.1, 2.2, 3.3), 'names', 'def']

[100, 'abc', 12.12, 'india', ['hyd', 'bang', 'ghy'], False]

Example –

x={[10,20,30]:'rakesh'}
print x
y={{'abc','def','xyz'}:'apurba'}
print y
z={(10,20,[100,200]):'ghy'}
print z

Output –

Traceback (most recent call last):

  File "C:/Users/om/PycharmProjects/Pythonn/if3.py", line 1, in <module>

    x={[10,20,30]:'rakesh'}

TypeError: unhashable type: 'list'

Example –

x={10:'abc',20:'def',30:'ijk',40:'def'}
print x
x[50]='hyd'
print x
x[40]='ghy'
print x
x.pop(30)
print x
x.popitem()
print x
del x[20]
print x
x.clear()
print x
del x

Output –

{40: 'def', 10: 'abc', 20: 'def', 30: 'ijk'}

{40: 'def', 10: 'abc', 20: 'def', 50: 'hyd', 30: 'ijk'}

{40: 'ghy', 10: 'abc', 20: 'def', 50: 'hyd', 30: 'ijk'}

{40: 'ghy', 10: 'abc', 20: 'def', 50: 'hyd'}

{10: 'abc', 20: 'def', 50: 'hyd'}

{10: 'abc', 50: 'hyd'}

{}

Example –

x={'barsha':60,'bikash':65,'apurba':58,'rimi':63}
print x
y=x.items()
print y
for p in y:
    print p[0],'\t',p[1]

Output –

{'bikash': 65, 'barsha': 60, 'rimi': 63, 'apurba': 58}

[('bikash', 65), ('barsha', 60), ('rimi', 63), ('apurba', 58)]

bikash        65

barsha        60

rimi             63

apurba       58

PROGRAM FOR ADDITION OF TWO 3X3 MATRIX

x=[[12,7,3],[4,5,6],[7,8,9]]
y=[[5,8,1],[6,7,3],[4,5,6]]
result=[[0,0,0],[0,0,0],[0,0,0]]
for i in range(len(x)):
    for j in range(len(x[0])):
        result[i][j]=x[i][j]+y[i][j]
for r in result:
    print r    
    

Output –

[17, 15, 4]

[10, 12, 9]

[11, 13, 15]

Example –

marks={}.fromkeys(['math','computer','java'],0)
print marks
for item in marks.items():
    print item
print sorted(marks.keys())

Output –

{'computer': 0, 'java': 0, 'math': 0}

('computer', 0)

('java', 0)

('math', 0)

['computer', 'java', 'math']

Example –

squares = {x*x*x for x in range(6)}
print squares
odd_square = {x:x*x for x in range(11) if x%2==1}
print odd_square
d={n:True for n in range(5)}
print d

Output –

set([0, 1, 8, 64, 27, 125])

{1: 1, 3: 9, 9: 81, 5: 25, 7: 49}

{0: True, 1: True, 2: True, 3: True, 4: True}