A dictionary in Python stores data as key-value pairs. In this article, we will discuss how to create an empty dictionary in Python and various Dictionary methods, such as copy(), get(), update(), etc.
A dictionary in Python is a changeable collection that is ordered and does not allow duplicates. Keys will be unique, and their values can be the same. Note that in Python 3.7 and later, dictionaries are ordered.
In this article…
In previous versions, such as Python 3.6 and older, dictionaries were unordered. You can create dictionaries using curly brackets {}, as shown below.
Syntax:
{key:value,........................,key:value}
Where key and value can be a string or an integer.
Python Empty Dictionary — Create, Add Data, and Initialize Values
Also Read: How to Exit Python Program [4 Methods]
Method 1: Using {}
We can create an empty dictionary using curly brackets ({}) with the assignment operator.
You can use the type() function to display the data type of a variable. In the example below, we will create and display an empty dictionary using the print() function.
Example:
#create an empty dictionary
my_dictionary={}
#display
print(my_dictionary)
#get the type
print(type(my_dictionary))
Output:
{}
<class 'dict'>
Method 2: Dict() method
Dict() is a Python method that you can use to create a dictionary. You can pass items from the dictionary as arguments in this method.
We will use the dict() method to create an empty dictionary.
dict()
Example:
#create an empty dictionary using dict my_dictionary=dict() #display print(my_dictionary) #get the type print(type(my_dictionary))
Output:
{}
<class 'dict'>
Create an empty dictionary with keys
Here, we will see how to create an empty dictionary with only keys and no values. We can use None to create empty values for each key in the dictionary.
Here’s the syntax for the same.
Syntax:
{'key':None,......}
Example:
In this example, we will create a dictionary with 5 integer keys and None values, and then display the dictionary.
#create an empty dictionary with 5 keys
my_dictionary={12: None, 34: None, 45: None,54:None,100:None}
#display
print(my_dictionary)
Output:
{12: None, 34: None, 45: None, 54: None, 100: None}
Create an empty nested dictionary
A data structure in which a dictionary contains multiple dictionaries is known as a nested dictionary. Now, we will see how to create an empty nested dictionary.
Syntax:
{key:{key:value},...............}
We can create this by specifying empty key-value pairs.
Example:
#create an empty nested dictionary
my_dictionary={ '': { }, '': { },'': { }, '': { },'': { }, '': { }}
#display
print(my_dictionary)
Output:
{'': {}}
How to Check If a Dictionary is Empty or Not
We can check whether the dictionary is empty using these methods.
Method 1: Using the if-else condition
This method will use if-else statements in Python to check if a dictionary is empty. First, we will define a dictionary variable and then use if-else statements to check if that dictionary is empty or not.
Let’s understand this with an example.
Example: In this example, we create two dictionaries – the first dictionary is empty, and the second dictionary will contain one key-value pair.
Next, we will use the if-else statements to display relevant messages.
#create an empty dictionary
my_dictionary1={}
#check if dictionary is empty
if(my_dictionary1):
print("Not empty")
else:
print("empty")
#create an dictionary with a key and value
my_dictionary2={'key':'codeitbro'}
#check if dictionary is empty
if(my_dictionary2):
print("Not empty")
else:
print("empty")
Output:
empty Not empty
Method 2: Using the not operator
You can also use the Python not operator to check whether a dictionary is empty. If the dictionary is empty, it returns True; otherwise, it returns False.
Example:
#create an empty dictionary
my_dictionary1={}
#check if dictionary is empty or not
print(not my_dictionary1 )
#create an dictionary with a key and value
my_dictionary2={'key':'codeitbro'}
#check if dictionary is empty or not
print(not my_dictionary2 )
Output:
True False
Method 3: Using bool()
The bool() function returns the Boolean value of a specified object. It will return false if:
- The object is 0
- The object is empty
- The object is none
- The object is false
This method will use the bool() Python function to check whether a dictionary is empty. If the dictionary is empty, it returns False; otherwise, it returns True.
Example: In this example, we create two dictionaries: the first dictionary is empty, and the second dictionary will contain one key-value pair.
After that, we will use the bool() function to check each of these dictionaries to determine if they are empty.
#create an empty dictionary
my_dictionary1={}
#check if dictionary is empty or not
print(bool( my_dictionary1) )
#create an dictionary with a key and value
my_dictionary2={'key':'codeitbro'}
#check if dictionary is empty or not
print(bool( my_dictionary2) )
Output:
False True
Method 4: Using len() with conditions
The len() will return the dictionary length (i.e., the number of key-value pairs in a dictionary). If the length equals 0, we can say that a dictionary is empty.
Example:
#create an empty dictionary
my_dictionary1={}
#check if dictionary is empty or not
if(len(my_dictionary1)==0):
print("empty")
else:
print("not empty")
#create an dictionary with a key and value
my_dictionary2={'key':'codeitbro'}
#check if dictionary is empty or not
if(len(my_dictionary2)==0):
print("empty")
else:
print("not empty")
Output:
empty not empty
Removing items from a dictionary
We can remove items from a dictionary using the clear() and pop() methods.
1. clear()
clear() will delete all the items from the dictionary. It doesn’t take any parameters.
Syntax:
my_dictionary.clear()
Where my_dictionary is the input dictionary.
Example: In this example, we will create a dictionary with 5 key-value pairs and clear all the key-value pairs from the dictionary.
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#display the dictionary
print(my_dictionary1)
#clear the items from the dictionary
my_dictionary1.clear()
#display the dictionary
print(my_dictionary1)
Output:
{1: 'php', 2: 'java', 3: 'html/css', 4: 'IOT', 5: 'Big-data'}
{}
Also Read: How To Automate Google Search With Python
2. pop()
We can delete a particular item from a dictionary by specifying the key.
Syntax:
my_dictinary.pop("key")
Where the key is the key label to be deleted.
Example:
In this example, we will remove the key-3
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#display the dictionary
print(my_dictionary1)
#clear the item with key 3
my_dictionary1.pop(3)
#display the dictionary
print(my_dictionary1)
Output:
{1: 'php', 2: 'java', 3: 'html/css', 4: 'IOT', 5: 'Big-data'}
{1: 'php', 2: 'java', 4: 'IOT', 5: 'Big-data'}
Python Dictionary Methods
Let’s explore some basic dictionary methods.
| Dictionary Function | Purpose |
| copy() | Copy items from one dictionary to another. It doesn’t modify the original dictionary. |
| get() | It returns the value associated with a specified key. |
| update() | Update dictionary items with items from another dictionary. |
| keys() | Get all the keys from a dictionary as a list. |
| values() | Get all the values from a dictionary as a list. |
| items() | Get all the key-value pairs of a dictionary as a tuple. |
1. copy()
The copy() method is used to copy items from one dictionary to another. The method returns a shallow copy of a dictionary item. It doesn’t take any arguments.
Syntax:
my_dictionary.copy()
Example: In this example, we will copy the contents of the first dictionary to the second dictionary.
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#display the dictionary
print(my_dictionary1)
#copy the dictionary
my_dictionary2=my_dictionary1.copy()
#display the dictionary
print(my_dictionary2)
Output:
{1: 'php', 2: 'java', 3: 'html/css', 4: 'IOT', 5: 'Big-data'}
{1: 'php', 2: 'java', 3: 'html/css', 4: 'IOT', 5: 'Big-data'}
2. get()
You can use the get() dictionary method to fetch an item with a specified key from a dictionary. It takes two parameters:
- Key: Required parameter. Here, you have to pass the key whose value you want to fetch.
- Value: Optional parameter. A default value to return if the key doesn’t exist in the dictionary.
Syntax:
my_dictionary.get('key')
Example: In this example, we will retrieve the values associated with the keys.
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#get the value from key-2
print(my_dictionary1.get(2))
#get the value from key-4
print(my_dictionary1.get(4))
#get the value from key-1
print(my_dictionary1.get(1))
Output:
java IOT php
3. update()
With the update() function, you can update the value in a dictionary based on a specific key. You can also use it to update a dictionary with items from another dictionary.
Syntax:
my_dictionary.update({'key':'new_value'})
Example: We will update the values based on the keys in this example.
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#update key 1 with "R lang"
my_dictionary1.update({1:"R lang"})
#update key 5 with "Spark"
my_dictionary1.update({5:"Spark"})
#display
print(my_dictionary1)
Output:
{1: 'R lang', 2: 'java', 3: 'html/css', 4: 'IOT', 5: 'Spark'}
We can also update multiple items using the update() method.
Example: We will update multiple values based on the keys in this example.
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#update key 1 with "R lang" and key 5 with "Spark"
my_dictionary1.update({1:"R lang",5:"Spark"})
#display
print(my_dictionary1)
Output:
{1: 'R lang', 2: 'java', 3: 'html/css', 4: 'IOT', 5: 'Spark'}
4. keys()
This method is used to get all the keys from a dictionary. It returns a view object and contains all the keys in a dictionary as a list.
Check this Python tutorial to check whether a key exists in a dictionary.
Syntax:
my_dictionary.keys()
Example:
In this example, we will get the keys from the dictionary.
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#display the keys
print(my_dictionary1.keys())
Output:
dict_keys([1, 2, 3, 4, 5])
5. values()
The values() Python method works similarly to the keys() method. It returns a view object that consists of the values from a dictionary as a list.
Syntax:
my_dictionary.values()
Example:
In this example, we will get the values from the dictionary.
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#display the values
print(my_dictionary1.values())
Output:
dict_values(['php', 'java', 'html/css', 'IOT', 'Big-data'])
6. items()
This Python dictionary method returns a view object that includes key-value pairs of a dictionary as a tuple.
Syntax:
my_dictionary.items()
Example:
In this example, we will get the items from the dictionary.
#create an dictionary
my_dictionary1={1:"php",2:"java",3:"html/css",4:"IOT",5:"Big-data"}
#display the items
print(my_dictionary1.items())
Output:
dict_items([(1, 'php'), (2, 'java'), (3, 'html/css'), (4, 'IOT'), (5, 'Big-data')])
Wrapping Up
In this tutorial, you learned how to create an empty dictionary in Python using various methods. Additionally, we covered how to create nested empty dictionaries and dictionaries with empty keys.
You also learned about different methods to check whether a dictionary is empty. And finally, we explored various Python dictionary methods, including copy(), get(), update(), and others.
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