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Few mistakes when using Python dictionary

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  • Last Updated : 06 Mar, 2019

Usually, A dictionary is a collection which is unordered, changeable and indexed. In Python, dictionaries are written with curly brackets, and they have keys and values. Each key-value pair in a Dictionary is separated by a ‘colon’, whereas each key is separated by a ‘comma’.




my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
print(my_dict)

Output:

{1: 'Geeks', 2: 'For', 3: 'Geeks'}

We generally use dictionaries to access the items with its key value, inside square brackets.




my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
print(my_dict[1])
print(my_dict[2])
print(my_dict[3])

Output:

Geeks
For
Geeks

The common operations of dictionaries are:

  • To get the values of the dictionary we use values() method.




    my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
    print(my_dict.values())

    Output:

    dict_values(['Geeks', 'For', 'Geeks'])
    
  • To get the keys of the dictionary we use keys() method.




    my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
    print(my_dict.keys())

    Output:

    dict_keys([1, 2, 3])
    
  • To add a new entry into the dictionary




    my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
    my_dict[4]='Python'
    print(my_dict)

    Output:

    {1: 'Geeks', 2: 'For', 3: 'Geeks', 4: 'Python'}
    
  • To change the value of the entry




    my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
    my_dict[3]='Python'
    print(my_dict)

    Output:

    {1: 'Geeks', 2: 'For', 3: 'Python'}
    
  • To delete an entry from dictionary




    my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
    del my_dict[3]
    print(my_dict)

    Output:

    {1: 'Geeks', 2: 'For'}
    
  • To copy the dictionary




    my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
    my_dict1 = my_dict
    print(my_dict1)

    Output:

    {1: 'Geeks', 2: 'For', 3: 'Geeks'}
    
  • To remove all entries.




    my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
    my_dict.clear()
    print(my_dict)

    Output:

    {}
    
  • To find the number of entries.




    my_dict = {1: 'Geeks', 2: 'For', 3:'Geeks'}
    z = len(my_dict)
    print(z)

    Output:

    3
    

Common mistakes while using dicts and overcomes

  • To access the value of the key, we generally use dict_name[key_name] instead we should use get() method to get rid of the exceptions thrown all throughout your code.
  • To update the value of the key, we generally use dict_name[key_name]=’new_value’ instead we should update(key=value) method to get rid of the exceptions thrown all throughout your code.
  • To copy the dictionary, we generally use dict_name = new_dict_name instead we should use copy() method to get rid of the exceptions thrown all throughout your code.

When not to use dicts

  • Dicts are useful but they’re not the only associative array structure in Python. Often there is a more specialised container type like set, tuple etc.
  • Numeric values with different types can be equal (e.g. 1 == 1.0), in which case they represent the same key.


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