environment windows7 (I want a Mac Book Pro 16inch) Visual Studio Code chrome python ver3.8.3
This article is written for beginners in programming and Python.
Creating a dictionary isn't difficult, but as a super beginner I make a few mistakes.
First of all, how to make a dictionary type.
{} Write the key and value in curly braces.
The key is described in {} with the name of the key and : (colon), and the value is described after : (colon).
One of the things I tend to make mistakes at this time is to enclose the keys and values in " " when writing strings.
I will forget ... Please be careful.
Write key 1: value 1, followed by, (comma) .
dict.py
{ "Key 1":"Value 1","Key 2":"Value 2","Key 3":"Value 3,・ ・ ・ ・ ・ ・}
Now that you have created a dictionary type, you can use this dictionary type. The value corresponding to the key is extracted as follows.
dict.py
academy_awards = {"Green book": 2019, "Chicago": 2003, "Titanic": 1998}
print(academy_awards["Green book"])
#2019
If you specify a key that is not set (does not exist) in the created dictionary type, an Error will occur.
However, if you use the .get method and specify a key that is not set (does not exist), then None
Will be returned.
dict.py
academy_awards = {"Green book": 2019, "Chicago": 2003, "Titanic": 1998}
print(academy_awards["Joker"])
#KeyError: 'Joker'
print(academy_awards.get("Joker"))
#None
If the .get method describes a string as the second argument, it will be the second if the key does not exist.
Returns an argument.
dict.py
academy_awards = {"Green book": 2019, "Chicago": 2003, "Titanic": 1998}
print(academy_awards.get("Joker", "The movie does not exist in the Best Picture"))
#The movie does not exist in the Best Picture
In addition, you can retrieve all keys, retrieve all values, and retrieve all keys and values.
Use .keys (), .values (), and .items (), respectively.
python.dict.py
academy_awards = {"Green book": 2019, "Chicago": 2003, "Titanic": 1998}
print(academy_awards.keys()) #Take out the key
#dict_keys(['Green book', 'Chicago', 'Titanic'])
print(academy_awards.values()) #Retrieve value
#dict_values([2019, 2003, 1998])
print(academy_awards.items()) #Take out everything
#dict_items([('Green book', 2019), ('Chicago', 2003), ('Titanic', 1998)])
fin
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