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python A dictionary is a powerful data structure used to store key-value pairs. Dictionaries are unordered, which means the order of key-value pairs does not matter. Keys in a dictionary are unique, which means that a key can only correspond to one value. The values in a dictionary can be any type of data, including lists, tuples, dictionaries, etc.
Create Dictionary
To create a dictionary, you can use two methods. The first way is to use curly braces {} and separate the key from the value with a colon :. For example:
my_dict = {"name": "John Doe", "age": 30, "city": "New York"}
The second method is to use the dict() function. The dict() function accepts an iterable object as argument and converts it into a dictionary. For example:
my_dict = dict([("name", "John Doe"), ("age", 30), ("city", "New York")])
Accessing elements in the dictionary
To access an element in a dictionary, you can use the key as an index . For example:
name = my_dict["name"] age = my_dict["age"] city = my_dict["city"]
You can also use the get() method to access elements in the dictionary. The get() method accepts two parameters: key and default value. If the key exists, the value corresponding to the key is returned; if the key does not exist, the default value is returned. For example:
name = my_dict.get("name") age = my_dict.get("age") city = my_dict.get("country", "N/A")
Add and delete elements in the dictionary
To add elements to the dictionary, you can use the [] operator or the update() method. The [] operator accepts two parameters: key and value. The update() method accepts an iterable object as a parameter and adds the key-value pairs in the iterable object to the dictionary. For example:
my_dict["country"] = "USA" my_dict.update({"state": "New York", "zip": 10001})
To delete elements from the dictionary, you can use the del keyword or the pop() method. The del keyword accepts a key as a parameter and deletes the value corresponding to the key from the dictionary. The pop() method accepts two parameters: key and default value. If the key exists, the value corresponding to the key is returned and removed from the dictionary; if the key does not exist, the default value is returned. For example:
del my_dict["country"] country = my_dict.pop("country", "N/A")
Traverse the dictionary
To traverse the dictionary, you can use a for loop. The for loop iterates through all key-value pairs in the dictionary. For example:
for key, value in my_dict.items(): print(key, value)
You can also use the keys() and values() methods to traverse the dictionary. The keys() method returns a list of all keys in the dictionary, and the values() method returns all values in the dictionary
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