Code used in this article
book_dict = {"price": 500, "bookName": "Python Design.", "weight": "250g"}
The first way:Use []
book_dict["owner"] = "tyson"
Description: specify the key in parentheses, assign a value, if the key does not exist, it is to add the element (if the key already exists, it is to modify the value corresponding to the key)
The second way:Use the update() method with a dictionary object as argument
book_dict.update({"country": "china"})
Description: Use dict's update() method to pass in a new dict object with a non-existing key! (If the key in this new dict object already exists in the current dictionary object, it will overwrite the value corresponding to the key.)
The third way:Use the update() method with keyword arguments
book_dict.update(temp = "Speechless.", help = "Help.")
Description: the same use of dict's update method, but passed the keyword parameter, the key does not exist is to add elements (key exists is to modify the value)
Note: the keyword parameter form, the key object can only be a string object
Fourth way:Use the update() method with a dictionary unpacking method as argument
my_temp_dict = {"name": "Mr. Wang.", "age":18}
book_dict.update(**my_temp_dict)
tantamount
book_dict.update(name="Mr. Wang.",age=18)
Note that dictionaries are completely unordered sets of mappings
1, the dictionary is unordered: when you traverse the dictionary elements, the order in which you add elements, and the order in which you access the elements are not related!
2, when you traverse a dictionary object, if you add elements in the same order as you, this is just a coincidence, the need for element-ordered dictionary see OrderedDict
Deleting Dictionary Elements
Method 1: del function
# Delete method 1: using the del function
del[aa['adress']]
print(aa) # {'talent': 60, 'english': 'english', 'price': 100, 'hhh': 'gogogo'}
Method 2: pop function
# Delete method 2: use the pop function and return the value
vv = ('Talent')
print(vv) # 60
print(aa) # {'English': 'english', 'price': 100, 'hhh': 'gogogo'}
Method 3: clear function
# clear method, removes all
()
print(aa) # {}, empty
dict (dictionary) in python:
1. Dictionary is another variable container model, where each key-value pair is separated by a colon (:), each key-value pair is separated by a comma (,), and the whole dictionary is surrounded by curly braces {};
2. Keys in a dictionary are generally unique, and a later key-value pair overwrites an earlier one if duplicated, although dictionary values need not be unique;
3. The value can take any data type, but the key must be of an immutable type, such as a string, a number or a tuple, but not a list because lists are mutable.
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