Python dictionary derivation

A key in a dictionary will not be repeated, and will be overwritten when the same key is assigned a second time.
Back to code: d={x:y for x in [1,3,5] for y in [2,4,6]}
x traverses once, y traverses 3 times,

< li > when x = 1, the change of d: < br / > d = {1} < br / > d = {and} < br / > d = {for} < / li > < li > when x = 3, the variation regularity of d: < br / > d = {1, 2} < br / > d = {1:4, 3:4} < br / > d = {} and set 1:6, < / li > < li > when x = 5, the variation regularity of d: < br / > d = {1, 3:2, 5-2} < br / > d = {1:4, 3:4, five} < br / > d = {1:6, set, but} < br / > so the end result is: {12 1:6, 3:6,} < blockquote >

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This answer quotes ChatGPT

This code is a dictionary derivation to create a dictionary where the key is the element in the list [1, 3, 5] and the value is the last element 6 in the list [2, 4, 6].

Specifically, the syntax of a dictionary derivation is {key_expression: value_expression for item in iterable}, where key_expression and value_expression are arbitrary expressions, and item is the element in iterable.

In this example, key_expression is x, value_expression is y, and item is the elements in the list [1,3, 5], i.e., 1, 3, and 5. In each iteration, y is the element in the list [2,4, 6], i.e. 2, 4, and 6, so a key-value pair is generated in each iteration, where the keys are 1,3, and 5, and the value is 6, because the last element in the list [2, 4, 6] is 6.

Therefore, the resulting dictionary is {1:6, 3:6, 5:6}. Note that since the key must be unique, there are only three keys in this dictionary, namely 1,3, and 5, but they all have the value 6.

When the program runs, run the first loop, x is 1,3,5. This is the key, and the y loop is the key. You get 2 as all the keys, you get 4, you replace 2, and so on, until you get 6.
{1:2,3:2,5:2} {1:4,3:4,5:4} {1:6,3:6,5:6}. Key change

Little Witch references parts of bing and GPT :
Dictionary derivation is a concise expression in Python that can be used to create new dictionaries. You don't need to use a for loop. In the code above, we create a new dictionary d whose keys are elements in [1,3,5] and whose values are elements in [2,4,6].

In dictionary comprehensions, we use the for statement to loop through the elements in the list, and then add those elements as keys and values to the newly created dictionary. Here, we first loop through the [1,3,5] lists, using them as the keys to the dictionary; Then loop through the list [2,4,6] as dictionary values.

Therefore, the resulting dictionary d is {1:6, 3.6, 5.6}. This is because for every element x in [1,3,5], a last element y is taken from [2,4,6] as its value. Since there are three elements in [2,4,6], the resulting dictionary d has all keys corresponding to the last value of 6.
The answer is not easy, so take it.

The dictionary cannot contain a key with the same name. The second time it appears will overwrite the first value, so the value will always be 6.

1：2 1：4 1：6
3：2 3：4 3：6
5：2 5：4 5：6

will only keep the result after.