Python dictionaries are versatile data structures that store key-value pairs. Here are some commonly used methods and operations associated with dictionaries:
1. Creating a Dictionary:
my_dict = {'key1': 'value1', 'key2': 'value2', 'key3': 'value3'}
2. Accessing Values:
value = my_dict['key1']
# or
value = my_dict.get('key1', default_value)
3. Adding or Updating Items:
my_dict['new_key'] = 'new_value' # Adding a new key-value pair
my_dict.update({'key1': 'new_value', 'key4': 'value4'}) # Updating existing or adding new key-value pairs
4. Removing Items:
del my_dict['key1'] # Remove a specific key-value pair
value = my_dict.pop('key2') # Remove and return the value for a given key
my_dict.clear() # Remove all items in the dictionary
5. Checking if a Key Exists:
if 'key1' in my_dict:
# Do something
6. Iterating Through Keys and Values:
for key in my_dict:
print(key, my_dict[key])
# or using items()
for key, value in my_dict.items():
print(key, value)
7. Dictionary Length:
length = len(my_dict)
8. Copying a Dictionary:
copy_dict = my_dict.copy() # Shallow copy
9. Merging Dictionaries:
new_dict = {**dict1, **dict2} # Requires Python 3.5 and above
# or
new_dict = dict1.copy()
new_dict.update(dict2)
10. Dictionary Comprehension:
squared_values = {key: value ** 2 for key, value in my_dict.items()}
11. Getting Keys and Values:
keys = my_dict.keys()
values = my_dict.values()
12. Set Default Value:
value = my_dict.setdefault('new_key', 'default_value')
13. Sorting:
Dictionaries are inherently unordered. To sort by keys or values, you can create a sorted list of items.
sorted_items = sorted(my_dict.items()) # Sort by keys
sorted_items_by_value = sorted(my_dict.items(), key=lambda x: x[1]) # Sort by values
These are just some of the commonly used methods with dictionaries in Python. Understanding these methods will help you effectively work with dictionaries in your Python programs.