Few mistakes when using Python dictionary

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’.

Python3 1==

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.

Python3 1==

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.

Python3 1==

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.

Python3 1==

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

Python3 1==

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

Python3 1==

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

Python3 1==

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

Output:

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

To copy the dictionary

Python3 1==

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.

Python3 1==

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

Output:

{}

To find the number of entries.

Python3 1==

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

Output:

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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Few mistakes when using Python dictionary

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