dictionary data type in python

2. Dictionary  Dictionaries are used to store data values in key:value pairs.  A dictionary is a collection which is unordered, changeable and does not allow duplicates. Dictionary is mutable.  Dictionaries are written with curly brackets, and have keys and values.  Key should be unique and immutable datatype.  If we try to assign a new value to same key prior value will be deleted and the new one will be stored.

3.  Values in the dictionary can be duplicated but key cannot be duplicated.  Key can be any immutable object like integer, float, character, complex,tuple.  Dictionary keys are case sensitive, same name but different cases of Key will be treated distinctly.

4.  Creating a dictionary: d={1:100, ’c’:20, (10,20,30):[100,200,300],4:30} print(d) O/P: {1:100, ’c’:20, (10,20,30):[100,200,300],4:30}  Values in the dictionary can be accessed using keys.  Eg:(d[‘c’]) O/P:20  In Python Dictionary, deletion of keys can be done by using the del keyword. Using del keyword, specific values from a dictionary as well as whole dictionary can be deleted.  Eg: del d[1] print(d) O/P:{’c’:20, (10,20,30):[100,200,300],4:30}

5. Dictionary Methods  clear():Removes all the elements from the dictionary  copy():Returns a copy of the dictionary  fromkeys():Returns a dictionary with the specified keys and value  get():Returns the value of the specified key  items():Returns a list containing a tuple for each key value pair  keys():Returns a list containing the dictionary's keys

6.  pop():Removes the element with the specified key  popitem():Removes the last inserted key-value pair  setdefault():Returns the value of the specified key. If the key does not exist: insert the key, with the specified value  update():Updates the dictionary with the specified key-value pairs  values():Returns a list of all the values in the dictionary

7. Examples  d = {1:100, 2.3:200, 10+20j:300, 'a': 'Python', (10,20,30):[100,200,3 00]} print(d.get('a')) O/P: Python  print(d.setdefault('b')) O/P: None  d1 = d.copy() # shallow copy of dictionary print(d1 is d) O/P:False  d={1:100,2.3:200,10+20j:300,'a':'Python',(10,20,30):[100,200,300]} d.pop(1) print(d) O/P:{2.3: 200, (10+20j): 300, 'a': 'Python', (10, 20, 30): [100, 200, 300]}

8.  d={1:100,2.3:200,10+20j:300,'a':'Python',(10,20,30):[100,200,300]} d.popitem() print(d) O/P: {1: 100, 2.3: 200, (10+20j): 300, 'a': 'Python'}

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