Decrypting Python Dictionaries: Understanding the Secrets of Key-Value Pairs

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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