Python Dictionary Functions in Day to Day Life

Hello all,

In this post, we will talk about some of the useful functions of a dictionary in python.
But before we dive into functions we will look for what is a dictionary in python.

What is Dictionary in Python?

• Dictionary is a Composite data type in Python. 
• Dictionary is all about pair.
• We can store different types of value in a dictionary.
• A Dictionary is very easy to use as it is mutable in nature.
• A Dictionary can grow and shrink as per our needs.
• A Dictionary can contain another dictionary, list or tuple as value.

Defining Dictionary :

You can define an empty dictionary by :

var dict = {}

Add Value and Delete Value from Dictionary :

• To add an entry in a dictionary we do like

var dict = {}
dict['key'] = value
print(dict)
{'key':value}

• If we try to add value with an already existing key, then python will replace the new value with old value for that key in the dictionary.
• To remove an entry from a dictionary 

var dict = {}
dict['key'] = value
print(dict)
{'key':value}

#to delete
del dict['key']
print(dict)
{}

Functions of Dictionary :

1.len()

2.keys()

3.values()

4.update()

5.clear()

1.len() :

• len() functions returns length of dictionary. 
• The length of the dictionary means a number of key, value pairs in a dictionary.

dict = {}
dict['key'] = "value";
print(len(dict))
# Output
# 1

2.keys() :

• keys() function is used when we want to list out all the keys of a dictionary.

dict = {}
dict['1'] = "One";
dict['2'] = "two";
dict['3'] = 3
print(dict.keys())

# Output
# dict_keys(['1', '2', '3'])

3.values() :

• values() function gathers all the values from the dictionary by separating keys, as a list.

dict = {}
dict['1'] = "One";
dict['2'] = "two";
dict['3'] = 3
print(dict.values())

# Output
# dict_values([3, 'two', 'One'])

4.update() :

• update() is very useful function of dictionary.
• This function is used to add new value/values in a dictionary.
• We can append two dictionaries with the help of update().

d1 = {'a': 10, 'b': 20, 'c': 30}
d2 = {'b': 200, 'd': 400}

d1.update(d2)
print(d1)
# Output
# {'a': 10, 'b': 200, 'c': 30, 'd': 400}

• In this example, you can notice that we already have 'b' as a key in our d1 dictionary so update() will not add 'b' as a new key instead of that it will overwrite the new value with old value for key 'b'. 

5.clear() :

• As the name suggests, clear() makes the dictionary empty.

d1 = {'a': 10, 'b': 20, 'c': 30}
print(d1)

d1.clear()
print(d1)

# Output
# {'c': 30, 'b': 20, 'a': 10}
# {}