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By Mostapha Amenchar in python —

Dictionaries in Python

A comprehensive guide to using Python dictionaries and different methods associated with it.

Dictionaries in Python

A data structure is a method to store and organize data. Python supports a number of important data structures including lists, sets ,tuples and dictionaries.

In this article we will focus on the Python Dictionaries. If you prefer to watch videos over text, check out the video here or scroll to the end.

Think of a phone book. You have names of people and the phone numbers associated to those people. A dictionary is exactly the data structure you need if you want to implement a phone book.

A phone book is nothing more than a collection of name: phone number pairs.

Similarly, a dictionary is a collection of key: value pairs.

  1. In python dictionaries, the key-value pair is separated by a colon(:). This pair is known as an item.
  2. Items are separated from each other by a comma (,).
  3. Different items are enclosed within a curly brace ({}) and all this forms a dictionary.

Syntax of a Python dictionary:

{ key1: value1, key2: value2,...,keyN: valueN}

Because dictionaries are indexed by keys, the dictionary key must meet the following two conditions:

  1. A key must be unique. Which means more than one entry per key is not allowed. When duplicate keys are encountered during assignment, the last assignment wins.
  2. The keys in a dictionary should be immutable types like integers, floats, boolean, strings and unicodes. Tuples can also be used as a key if it does not contain a mutable structure such as a list.
# This runs fine
dict_example = {
    ("title"):"Python Dictionary"
}
print(dict_example)
>>> {'title': 'Python Dictionary'}

# This throws an error
dict_example = {
    ([1,2,3]):"Python Dictionary"
}
print(dict_example)
>>> Traceback (most recent call last):
    File <input>, line 2, in <module>
      ([1,2,3]):"Python Dictionary"
    TypeError: unhashable type: 'list'

Unlike keys, dictionary values have no restrictions. They can be any arbitrary python object.

Topics Covered

  1. Creating a dictionary
  2. Accessing dictionary keys, values and items
  3. Modifying a dictionary
  4. Copying a dictionary
  5. Nested dictionary
  6. Problems to Solve

Creating a dictionary

In order to create a python dictionary, you can either use the curly bracket syntax or the dict() constructor.

Curly bracket syntax

A pair of empty braces {} create an empty dictionary.

empty_dict = {}
print(empty_dict)
>>> {}

print(type(empty_dict))
>>> <class 'dict'>

Placing a comma-separated items (key: value) pairs within the braces {} adds initial items to the dictionary.

capital_dict = {"India": "New Delhi",
		        "Pakistan": "Islamabad",
		        "Nigeria": "Abuja",
		        "Zambia": "Lusaka"}
print(capital_dict)
>>> {'India': 'New Delhi', 'Pakistan': 'Islamabad', 'Nigeria': 'Abuja', 'Zambia': 'Lusaka'}

Merging existing dictionaries is also very easy.

capital_dict_1 = {"India": "New Delhi",
		          "Pakistan": "Islamabad",
		          "Nigeria": "Abuja",
		          "Zambia": "Lusaka"}

capital_dict_2 = {"Peru": "Lim", 
                  "Ghana": "Accra"}

capital = {**capital_dict_1, **capital_dict_2}
print(capital)
>>> {'India': 'New Delhi', 'Pakistan': 'Islamabad', 
     'Nigeria': 'Abuja', 'Zambia': 'Lusaka', 
	 'Peru': 'Lim', 'Ghana': 'Accra'}

Using dict() constructor

The dict() constructor build dictionaries directly from sequences of (key: value) pairs.

In order to create an empty dictionary, you can call dict() with no arguments.

capital_dict = dict()
print(capital_dict)
>>> {}

print(type(capital_dict))
>>> <class 'dict'>

The dict() constructor can be used to create python dictionaries from the following options.

  • keyword arguments
capital_dict = dict(India="New Delhi",
		            Pakistan="Islamabad",
		            Nigeria="Abuja",
		            Zambia="Lusaka")
print(capital_dict)
>>> {'India':'New Delhi','Pakistan': 'Islamabad','Nigeria':'Abuja','Zambia': 'Lusaka'}
  • Single iterable of key: value pairs
# Passing a list into the dict() constructor
capital_dict = dict([("India","New Delhi"),
		             ("Pakistan","Islamabad"),
		             ("Nigeria","Abuja"),
		             ("Zambia","Lusaka")])
print(capital_dict)
>>> {'India': 'New Delhi','Pakistan': 'Islamabad','Nigeria': 'Abuja','Zambia': 'Lusaka'}
  • Single dictionary and keyword arguments
capital_dict = dict(
                    {"India":"New Delhi", "Pakistan":"Islamabad"},
		             Nigeria = "Abuja",Zambia= "Lusaka"
                   )
print(capital_dict)
>>> {'India': 'New Delhi','Pakistan': 'Islamabad','Nigeria': 'Abuja','Zambia': 'Lusaka'}
  • Single iterable of key: value pairs and keyword arguments
capital_dict = dict([("India","New Delhi"), ("Pakistan","Islamabad")],
		            Zambia = "Lusaka")
print(capital_dict)
>>> {'India': 'New Delhi','Pakistan': 'Islamabad','Zambia': 'Lusaka'}

Merging existing dictionaries are only possible if keys are of the string type.

capital_dict_1 = dict([("India","New Delhi"),
		               ("Pakistan","Islamabad")])
capital_dict_2 = dict(Nigeria = "Abuja",
		              Zambia = "Lusaka")
capital = dict(**capital_dict_1,**capital_dict_2)

print(capital)
>>> {'India': 'New Delhi', 'Pakistan': 'Islamabad', 'Nigeria': 'Abuja', 'Zambia': 'Lusaka'}

Dictionary comprehension

A dictionary comprehension takes the form {key:value for (key,value) in iterable}. Let’s look at some examples.

  • From one list:
lst = [0,1,2,3,4,5]
dic = {x : x**2 for x in lst}

print(dic)
>>> {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
  • From two parallel lists
countries  = ["India", "Pakistan", "Nigeria", "Zambia", "Ghana"]
capitals = ["New Delhi", "Islamabad", "Abuja", "Lukasa", "Accra"]

capital_dict = {key:value for key,value in zip(Countries,Capitals)}
print(capital_dict)
>>> {'India':'New Delhi','Pakistan':'Islamabad','Nigeria':'Abuja','Zambia': 'Lukasa','Ghana':'Accra'}

Transformation of an existing dictionary to a new dictionary

During transformation of an existing dictionary to a new dictionary, items within the existing dictionary can be conditionally included in the new dictionary and each item can be transformed as needed.

We will take the following dictionary as an example.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}

For information: GDP is acronym of Gross domestic Product. GDP is a measure of the value of the total production in a country, usually in a given year, The ideal GDP growth rate is between 2 and 3%.*

Example 1:

GDP_2017 = {"India": 6.6,"Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_growth_rate = {key:("ideal" if 2 < GDP_2017[key] < 3 else "not ideal")for key in GDP_2017}

print(GDP_growth_rate)
>>> {'India': 'not ideal',
     'Zambia': 'not ideal', 
     'Nigeria': 'not ideal', 
	 'Peru': 'ideal', 
     'Ghana': 'not ideal'}

Example 2:

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_ideal= {key:GDP_2017[key] for key in GDP_2017 \
            if 2 < GDP_2017[key] < 3}

print(GDP_ideal)
>>> {'Peru': 2.5}

Example 3:

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_ideal = {key:GDP_2017[key] for key in GDP_2017 \ 
             if GDP_2017[key] > 2 if GDP_2017[key] < 3}

print(GDP_ideal)
>>> {'Peru': 2.5}

Example 4:

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_not_ideal = {key:GDP_2017[key] for key in GDP_2017 \
                 if GDP_2017[key] < 2 or GDP_2017[key] > 3}

print(GDP_not_ideal)
>>> {'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Ghana': 8.5}

Accessing dictionaries

When working with a python dictionary, it is sometimes necessary to access dictionary data such as keys, values and items (key-value pairs). Access to this data can take place in various ways.

The methods below can be applied to access a certain value from a dictionary.

Accessing keys

Using Square brackets

To access dictionary elements, you can use square brackets along with the key to obtain its value.

Example 1:

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}

print(GDP_2017["India"])
>>> 6.6

Example 2:

If the given key does not exist in the dictionary, Python raises a Key Error exception.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}

print(GDP_2017["America"])
>>>	Traceback (most recent call last):
 	File "<input>", line 1, in <module>
    GDP_2017["America"]
	KeyError: 'America'

Example 3:

Catching the exception is another way to handle missing keys.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
try:
    GDP_2017["America"]
except KeyError:
    print("No valid key! Please try again....")
    
>>> No valid key! Please try again....

get(key , default ) method

Example 1:

The get(key) method returns the associated value for the given key if key is in the dictionary, else it returns the default value.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
desired_key = GDP_2017.get("India","No valid key! Please try again....")
print(desired_key)
>>> 6.6

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
desired_key = GDP_2017.get("America","No valid key! Please try again....")
print(desired_key)
>>> No valid key! Please try again....

Example 2:

If default value is not passed, it returns None. Hence this method never raises a Key Error.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
desired_key = GDP_2017.get("America")
print(desired_key)
>>> None

Built in methods

  • Accessing all values()

The values() method can be used to loop over only values in a dictionary.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
for value in GDP_2017.values():
	print(value)
>>>	6.6
	4.1
	0.8
	2.5
	8.5
  • Accessing all keys()

The keys() method can be used to loop over keys in the dictionary.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
for key in GDP_2017.keys():
	print(key)	
>>>	India
	Zambia
	Nigeria
	Peru
	Ghana
  • Accessing all items()

The items() method can be used to loop over both the keys and values of a dictionary.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
for key,value in GDP_2017.items():
	print(key,value)
	
>>>	India 6.6
	Zambia 4.1
	Nigeria 0.8
	Peru 2.5
	Ghana 8.5
  • Using list comprehension to access all keys
GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
key = [key for key in GDP_2017]
print(key)
>>>	['India', 'Zambia', 'Nigeria', 'Peru', 'Ghana']
  • Using list comprehension to access all values
GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
value = [GDP_2017[key] for key in GDP_2017]
print(value)
>>>	[6.6, 4.1, 0.8, 2.5, 8.5]
  • Using list comprehension to access all keys and values
GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
item = [(key,GDP_2017[key]) for key in GDP_2017]
print(item)
>>>	[('India', 6.6), ('Zambia', 4.1), ('Nigeria', 0.8), ('Peru', 2.5), ('Ghana', 8.5)]
  • Using list comprehension + dictionary.keys() to access all keys
GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
key = [key for key in GDP_2017.keys()]
print(key)
>>>	['India', 'Zambia', 'Nigeria', 'Peru', 'Ghana']
  • Using list comprehension + dictionary.values() to access all values
GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
value = [value for value in GDP_2017.values()]
print(value)
>>>	[6.6, 4.1, 0.8, 2.5, 8.5]
  • Using list comprehension + dictionary.items() to access all keys and values
GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
item = item = [item for item in GDP_2017.items()]
print(item)
>>>	[('India', 6.6), ('Zambia', 4.1), ('Nigeria', 0.8), ('Peru', 2.5), ('Ghana', 8.5)]

Modifying a dictionary

Python offers a number of methods to modify a dictionary.

Removing an item from a dictionary

In Python, there are multiple methods for removing dictionary items.

  • del() method

The del keyword can be used to delete an individual item.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
del GDP_2017["Peru"]
print(GDP_2017)
>>>	{'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Ghana': 8.5}

It can also be used to delete an entire dictionary.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
del GDP_2017
print(GDP_2017)
>>>	Traceback (most recent call last):
 	File <input>, line 1, in <module>
    GDP_2017
	NameError: name 'GDP_2017' is not defined
  • pop() method

The pop() method removes an item with the provided key and returns the value of that key.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
popped_value = GDP_2017.pop("Peru")
print(popped_value)
>>>	2.5

print(GDP_2017)
>>>	{'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Ghana': 8.5}
  • popitem() method

Since Python3.7, the popitem() method removes the last inserted item. In all the previous versions, popitem() used to remove a random key-value pair.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
print(GDP_2017.popitem())
>>>	('Ghana', 8.5)

print(GDP_2017)
>>>	{'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5}
  • clear() method

The clear() method removes all items from a dictionary.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_2017.clear()

print(GDP_2017)
>>>	{}

Adding new key-values to a dictionary

  • Assignment operator with dictionary key

Adding an item to a python dictionary is done by using a new index key and assigning a value to it.

GDP_2017 = {"India": 6.6, "Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_2017["Pakistan"]= 5.7

print(GDP_2017)
>>>	{'India': 6.6,'Zambia': 4.1,'Nigeria':0.8,'Peru':2.5,'Ghana':8.5, 'Pakistan':5.7}
  • update() method

The update() method updates the dictionary with the elements from another dictionary or from an iterable of key-value pairs.

GDP_2017 = {"India": 6.6, "Zambia": 4.1}
Other = {"Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_2017.update(Other)

print(GDP_2017)
>>>	{'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}

If key already exists, then the update() method will updates its value.

GDP_2017 = {"India": 6.6, "Zambia": "????"}
Other = {"Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_2017.update(Other)
print(GDP_2017)
>>>	{'India': 6.6,'Zambia': 4.1,'Nigeria': 0.8,'Peru': 2.5,'Ghana': 8.5}
  • Asterisk operator

The ** operator merges an old dictionary and new key-value pairs in another dictionary

GDP_2017 = {"India": 6.6, "Zambia": "????"}
Other = {"Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_NEW = {**GDP_2017,**Other}

print(GDP_NEW)
>>>	{'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}

Sorting a dictionary

Sometimes you may wish to sort the dictionary either by key or by value.

  • Sorting by keys
GDP_2017 = {'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}
GDP_2017_sorted = {k:GDP_2017[k] for k in sorted(GDP_2017.keys())}

print(GDP_2017_sorted)
>>>	{'Ghana': 8.5, 'India': 6.6, 'Nigeria': 0.8, 'Peru': 2.5, 'Zambia': 4.1}
  • Sorting by values
GDP_2017 = {'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}
GDP_2017_sorted = {k:v for k,v in sorted(GDP_2017.items(),key=lambda x: x[1])}

print(GDP_2017_sorted)
>>>	{'Nigeria': 0.8, 'Peru': 2.5, 'Zambia': 4.1, 'India': 6.6, 'Ghana': 8.5}

Copying a dictionary

There are two methods to make a copy of an existing python dictionary. Both two methods result in an identical dictionary which is a distinct object.

  • copy() method
GDP_2017 = {'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}
GDP_2017_copy = GDP_2017.copy()

print(GDP_2017_copy)
>>>	{'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}
print(id(GDP_2017) == id(GDP_2017_copy))
>>>	False
  • Passing an existing dictionary to dict() constructor method
GDP_2017 = {'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}
GDP_2017_copy = dict(GDP_2017)

print(GDP_2017_copy)
>>>	{'India': 6.6, 'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}
print(id(GDP_2017) == id(GDP_2017_copy))
>>>	False

Nested dictionary

In Python, a nested dictionary is a collection of dictionaries within one single dictionary.

Creation of a nested dictionary

GDP_Africa = {"Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_Asia = {"India": 6.6, "Pakistan": 5.7}

GDP_nested = {"GDP_Africa" :{"Zambia": 4.1,"Nigeria":0.8,"Peru":2.5,"Ghana": 8.5},
                "GDP_Asia" : {"India": 6.6, "Pakistan": 5.7}
             }

Nested dictionaries can also be updated by adding or removing an element. To access a key or a dictionary in a nested dictionary, use the [] syntax indexing.

Adding elements to a nested dictionary

Example 1:

GDP_Africa = {"Zambia": 4.1,"Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5}
GDP_Asia = {"India": 6.6, "Pakistan": 5.7}
GDP_nested = {"GDP_Africa" : GDP_Africa,
                 "GDP_Asia": GDP_Asia}
GDP_nested["GDP_Africa"]["South Africa"] = 1.3

print(GDP_nested)
>>>	{'GDP_Africa': {'Zambia': 4.1, 
                    'Nigeria': 0.8, 
                    'Peru': 2.5,
                    'Ghana': 8.5, 
                    'South Africa': 1.3}, 
     'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}}

Example 2:

GDP_nested = {"GDP_Africa" :{"Zambia": 4.1, "Nigeria": 0.8,"Peru":2.5, "Ghana": 8.5},
                 "GDP_Asia": {"India": 6.6, "Pakistan": 5.7}}
GDP_nested["GDP_America"]={"Peru": 2.5}

print(GDP_nested)
>>>	{'GDP_Africa': {'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}, 
       'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 'GDP_America': {'Peru': 2.5}}

Accessing elements in a nested dictionary

Let’s take the example of the following dictionary.

GDP_nested = {'GDP_Africa': {'Zambia': 4.1, 
                             'Nigeria': 0.8, 
                             'Peru': 2.5, 
                             'Ghana': 8.5},  
                'GDP_Asia': {'India': 6.6, 
                             'Pakistan': 5.7}, 
             'GDP_America': {'Peru': 2.5}}

Example 1: How to access GDP of Zambia ?

GDP_nested = {'GDP_Africa': {'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5},     
                'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 
             'GDP_America': {'Peru': 2.5}}
GDP_Zambia = GDP_nested["GDP_Africa"]["Zambia"]

print(GDP_Zambia)
>>>	4.1

Example 2: How to access GDP_Asia?

GDP_nested = {'GDP_Africa': {'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}, 
                'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 
             'GDP_America': {'Peru': 2.5}}
GDP_Asia = GDP_nested["GDP_Asia"]

print(GDP_Asia)
>>>	{'India': 6.6, 'Pakistan': 5.7}

Deleting elements from a nested dictionary

Example 1: Delete GDP of Zambia

To remove an element from a nested dictionary, use the del() method.

GDP_nested = {'GDP_Africa': {'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}, 
                'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 
             'GDP_America': {'Peru': 2.5}}
del(GDP_nested["GDP_Africa"]["Zambia"])

print(GDP_nested)
>>>	{'GDP_Africa': {'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}, 
       'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 
    'GDP_America': {'Peru': 2.5}}

Example 2: Delete GDP of Africa

To remove a dictionary from a nested dictionary there are two methods available in python.

  • del() method
  GDP_nested = {'GDP_Africa': {'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}, 
                  'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 
               'GDP_America': {'Peru': 2.5}}

  del(GDP_nested["GDP_Africa"])
  print(GDP_nested)
  >>> {'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 'GDP_America': {'Peru': 2.5}}
  • pop() method
  GDP_nested = {'GDP_Africa': {'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}, 
                  'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 
               'GDP_America': {'Peru': 2.5}}
  pop_value = GDP_nested.pop("GDP_Africa")

  print(pop_value)
  >>> {'Zambia': 4.1, 'Nigeria': 0.8, 'Peru': 2.5, 'Ghana': 8.5}
  print(GDP_nested)
  >>> {'GDP_Asia': {'India': 6.6, 'Pakistan': 5.7}, 'GDP_America': {'Peru': 2.5}}

The pop() method returns the removed dictionary.

Problems

  1. Write a Python code to merge 2 dictionaries as shown below.

     capital_dict_1 = {"India": "New Delhi",
           "Pakistan": "Islamabad",
           "Nigeria": "Abuja",
           "Zambia": "Lusaka"}

 capital_dict_2 = {"Peru": "Lim", 
           "Ghana": "Accra"}

Solution - Use the asterisk operator

  1. Write a Python program to sort a dictionary by value.

Solution

  1. Write a Python script to check whether a given key already exists in a dictionary.

Solution - Use the get() method

  1. Write a Python program to sum all the items in a dictionary.

Hope you enjoyed this article on Python dictionaries. If you have any questions, make sure to put them in the comments section.

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