Python Dictionary Methods with Examples

1. Introduction

In this tutorial, we will learn the usage of common Dictionary methods in Python with examples.

Python dictionaries are an integral part of the language. They allow us to store and manage data in key-value pairs. To efficiently use dictionaries, Python provides a variety of methods that perform different operations on dictionaries, from adding and removing items to merging two dictionaries together.

Python Dictionary Methods:

- clear(): Removes all items from the dictionary.

- copy(): Returns a shallow copy of the dictionary.

- fromkeys(): Creates a new dictionary with keys from seq and values set to value.

- get(): Returns the value for a key if it exists in the dictionary.

- items(): Returns a view object that displays a list of dictionary's (key, value) tuple pairs.

- keys(): Returns a view object that displays a list of all the keys.

- pop(): Removes and returns an element from a dictionary with the provided key.

- popitem(): Removes the last inserted key-value pair.

- setdefault(): Returns the value of a key if the key is in the dictionary; if not, inserts the key with the specified value.

- update(): Updates the dictionary with elements from another dictionary object or from an iterable of key-value pairs.

- values(): Returns a view object that displays a list of all the values in the dictionary.

2. Program Steps

1. Create a dictionary for demonstration.

2. Perform and print the result of each method operation on the dictionary.

3. Code Program

# Create a dictionary
my_dict = {'a': 1, 'b': 2, 'c': 3}

# Use clear()
my_dict.clear()
print(f"After clear(): {my_dict}")

# Use copy()
my_dict = {'a': 1, 'b': 2, 'c': 3}
dict_copy = my_dict.copy()
print(f"After copy(): {dict_copy}")

# Use fromkeys()
keys = ['a', 'b', 'c']
default_value = 0
new_dict = dict.fromkeys(keys, default_value)
print(f"After fromkeys(): {new_dict}")

# Use get()
value_a = my_dict.get('a')
print(f"After get(): {value_a}")

# Use items()
dict_items = my_dict.items()
print(f"After items(): {dict_items}")

# Use keys()
dict_keys = my_dict.keys()
print(f"After keys(): {dict_keys}")

# Use pop()
value_popped = my_dict.pop('b')
print(f"After pop(): {value_popped}, {my_dict}")

# Use popitem()
item_popped = my_dict.popitem()
print(f"After popitem(): {item_popped}, {my_dict}")

# Use setdefault()
default = my_dict.setdefault('d', 4)
print(f"After setdefault(): {default}, {my_dict}")

# Use update()
second_dict = {'e': 5, 'f': 6}
my_dict.update(second_dict)
print(f"After update(): {my_dict}")

# Use values()
dict_values = my_dict.values()
print(f"After values(): {dict_values}")

Output:

After clear(): {}
After copy(): {'a': 1, 'b': 2, 'c': 3}
After fromkeys(): {'a': 0, 'b': 0, 'c': 0}
After get(): 1
After items(): dict_items([('a', 1), ('b', 2), ('c', 3)])
After keys(): dict_keys(['a', 'b', 'c'])
After pop(): 2, {'a': 1, 'c': 3}
After popitem(): ('c', 3), {'a': 1}
After setdefault(): 4, {'a': 1, 'd': 4}
After update(): {'a': 1, 'd': 4, 'e': 5, 'f': 6}
After values(): dict_values([1, 4, 5, 6])

Explanation:

Each method is called on the my_dict dictionary.

- clear() empties the dictionary.

- copy() creates a copy that is assigned to dict_copy.

- fromkeys() creates a new dictionary with specified keys and default value.

- get() retrieves the value for key 'a'.

- items(), keys(), and values() return view objects containing the dictionary's items, keys, and values, respectively.

- pop() removes the key 'b' and returns its value.

- popitem() removes and returns the last key-value pair.

- setdefault() inserts key 'd' with a default value of 4 since 'd' is not already in the dictionary.

- update() adds key-value pairs from second_dict to my_dict.

Each operation's result is printed to show the effect of the method on the dictionary.