The python dictionary has a set of in-built methods used to perform various tasks in the dictionary. Python dictionary is a collection of unordered elements. Elements in the dictionary are in the form of key-value pairs each key having its corresponding value.
Using some of the in-built dictionary methods such as items(), key(), values() we can access our desired key-value pairs. Using the get() method we can get a value for a specified key. If a key doesn’t exist in the dictionary it returns the default value None. Moreover, we can create a new dictionary from the given iterable objects using some Python Dictionary methods.
Furthermore, we can update, copy the dictionary using update() and copy() methods. On the other hand, we can delete all the key-value pairs using the clear() method. If you want to delete the element with the specified key, it is possible by using the pop() method of the Python dictionary.
Below are the most used dictionary methods in Python, Click on each link from the below table to understand with examples.
1. Dictionary Methods
| Methods | Dictionary Method Description |
|---|---|
| clear() | Delete all the key: value pairs from the dictionary |
| copy() | Returns a shallow copy of the dictionary |
| fromkeys() | creates a new dictionary from the given iterable objects |
| get() | Returns the value of the specified key |
| items() | Returns a view object that allows a dynamic view of dictionary elements as a list of key, value (tuple) pairs. |
| keys() | Returns a view object which contains a list of all keys related to the dictionary. |
| pop() | Removes the element with the specified key |
| popitem() | Removes the last inserted key-value pair |
| setdefault() | It returns a value if the key is present. Otherwise, it inserts the key with the default value into the dictionary. The default value of the key is None. |
| update() | Updates the dictionary with the specified key-value pairs |
| values() | Returns a view object that contains a list of all the values stored in the dictionary. |
2. Dictionary Methods Examples
2.1 clear()
clear() method is used to remove all elements from the python dictionary. When you have a dictionary with too many elements, deleting all elements of the dictionary one after another is a very time taken process, so use clear() method to delete all elements at once rather than deleting elements one by one. For example,
# Delete all key: value pairs from the dictionary
technology = { 'course':'python', 'fee': 4000, 'duration': '60 days' }
technology.clear()
print("Technology:", technology)
# Returns empty dictionary
# Technology: {}
2.2 copy()
copy() method is used to get a copy of the python dictionary. You can copy the Python dictionary in different ways. copy() method does the shallow copy of the dictionary. For Example,
# Using copy() method copy the technology dictionary
technology = { 'course':'python', 'fee': 4000, 'duration': '60 days' }
new_technology=technology.copy()
print("Original technology: ",technology)
print("New technology: ",new_technology)
# Output:
# Original technology: {'course': 'python', 'fee': 4000, 'duration': '60 days'}
# New technology: {'course': 'python', 'fee': 40000, 'duration': '60 days'}
2.3 fromkeys()
fromkeys() creates a new Python dictionary from the given iterable objects such as string, list, tuple, and set as keys and with a specified value. If no value is specified to value param, the values of keys are set to None by default. For example,
# Create a dictionary using fromkeys()
technology ={"course","fee","duration"}
dictionary=dict.fromkeys(technology ,'language')
print(dictionary)
# Output:
# {'fee': 'language', 'course': 'language', 'duration': 'language'}
2.4 get()
get() method is used to get the value of the element with the specified keys from the Python dictionary. This method takes optional value param which is used to return the default value when a key is not present.
# Using get() method to get the value from dictionary
technology={'course': 'python', 'fee': 4000}
print('course:', technology.get('course'))
# course: python
print('fee:',technology.get('fee'))
# fee: 4000
2.5 items()
items() method is used to return a view object of the python dictionary elements as tuples in a list. The items in the dictionary are unordered and mutable hence, they can be changed, removed, and added after the creation of the dictionary. However, the items cannot duplicate within the same dictionary.
# Using the items() to get dictionary elements
technology = { 'course':'python', 'fee': 4000, 'duration': '60 days' }
print(technology.items())
# Output:
# dict_items([('course', 'python'), ('fee', 4000), ('duration', '60 days')])
2.6 keys()
Python dictionary keys() method is used to get the list of all the keys in the dictionary. The keys() method returns a view object which contains a list of all keys related to the Python dictionary.
# Update the keys() method if update the dictionary
technology={"Course":"python","Fee":4000,"Duration":"60 days"}
print(technology.keys())
# Output:
# dict_keys(['Course', 'Fee', 'Duration'])
technology.update({"tutor": "Richard"})
print(technology.keys())
# Output:
# dict_keys(['Course', 'Fee', 'Duration', 'tutor'])
2.7 pop()
The pop() method of Python dictionary (dict) is used to remove the element from the dictionary by dict key and return the value related to the removed key. If a key does not exist in the dictionary and the default value is specified, then returns the default value; else throws a KeyError. For example,
# Delete the key element using pop() method
technology = { 'course':'python', 'fee': 4000, 'duration': '60 days' }
item=technology.pop('fee')
print("Popped value is:",item)
print("The dictionary is:" ,technology)
# Outputs:
# Popped value is: 4000
# The dictionary is: {'course': 'python', 'duration': '60 days'}
2.8 popitem()
popitem() is a built-in method in the python dictionary that is used to remove and return the last key-value pair from the dict. It follows the Last In First Out approach. If the dictionary is empty, it returns a KeyError.
# Remove last item using popitem()
technology = {'course': 'python', 'fee': 4000, 'duration': '45 days'}
element=technology.popitem()
print("Removed element:",element)
print(technology)
# Output:
# Removed element: ('duration', '45 days')
# {'course': 'python', 'fee': 4000}
2.9 setdefault()
Using the setdefault() method we can set the default value to the key of the Python dictionary. It returns a value if the key is present in the dictionary. Otherwise, it inserts the key with the value specified into the dictionary. If a value is not specified, it set the default value None.
# Key is not present in the dictionary, value not specified
technology = {"course": "python", "fee": 4000}
duration = technology.setdefault("duration")
print('Technology:', technology)
print('Duration:',duration)
# Output: Technology:
# {'course': 'python', 'fee': 4000, 'duration': None}
# Duration: None
2.10 update()
Using the Python Dictionary update() method we can update the dictionary by using another dictionary or an iterable of key-value pairs(such as a tuple). If the key is already present, this method updates the existing key with the new value from the iterable value. For example,
# Using update() update the dictionary
Technology = {'course': 'python', 'fee':4000}
Technology.update({'duration':'45days'})
print("Updated Technology:",Technology)
# Outputs:
# Updated Technology: {'course': 'python', 'fee': 4000, 'duration': '45days'}
2.11 values()
Python dictionary values() method returns a view object that contains a list of all values stored in the dictionary. This method is useful if you want to iterate over only the values in the dictionary. Any changes in the dictionary will reflect in the view object.
# Using Values() to get values from the dictionary
technology = { 'course':'python', 'fee': 4000, 'duration': '60 days' }
print(technology.values())
# Outputs:
# dict_values(['python', 4000, '60 days'])
3. Conclusion
In this article, I have explained Python dictionary methods. As well, I have explained the benefits of these methods with working examples and output. I hope this gives you a better understanding of what you can do with python dictionary.
Happy Learning !!
Related Articles
- dict.get() method
- dict.pop() method
- dict.clear() method
- dict.items() method
- dict.fromkeys() method
- dict.copy() method
- dict.values() method
- dict.setdefault() method
- dict.popitem() method
- dict.update() method