golang map added

Golang is an advanced programming language that combines the high performance of C language with the simplicity and ease of use of Python language. It has developed rapidly and has become one of the most widely used programming languages ​​in the industry. In this article, we will discuss the addition operation of map in Golang.

Map is a data structure used to store key-value pairs. It is similar to Dictionary in Python, HashMap in Java, etc. Map is a reference type in Golang and can be initialized using the make function. Unlike an array, the length of a Map can grow dynamically, making it ideal for storing an indeterminate number of key-value pairs.

In Golang, the adding operation of Map is divided into two parts. The first part is to create a Map type variable, and the second part is to add data to the Map.

First, we need to declare a variable of Map type. The syntax is as follows:

var m map[keyType]valueType

where keyType represents the type of key in the Map and valueType represents The type of values ​​in the Map. For example, if we want to create a Map where the key is a string type and the value is an integer type, the declaration statement is as follows:

var m map[string]int

It should be noted that , the declaration here does not allocate memory space for the Map, so the make function must be used to initialize the Map before using the Map. The syntax for using the make function is as follows:

m = make(map[keyType]valueType)

Or you can use short declaration syntax to quickly create a Map:

m := make( map[string]int)

Now that we have created a Map type variable m, we can add key-value pairs to m. The addition operation using Map requires the use of the subscript operator [], which is similar to the array subscript operator in other languages. When we add a new element to the Map, we need to give the key and value of the element. Here is a sample code:

m["one"] = 1
m["two"] = 2

In this example, we add two to the Map Key-value pairs, the keys are "one" and "two", and the values ​​are 1 and 2 respectively. If we want to modify the elements in the Map, we can use the same syntax.

For keys that already exist in the Map, we can get their values ​​through the subscript operator. The following is a sample code:

fmt.Println(m["one"]) // Output 1
fmt.Println(m["two"]) // Output 2

When we use the subscript operator to obtain a key that does not exist in the Map, the Map will return a zero value of the value type corresponding to the key. For example, if we use the following line of code to get the value with the key "three":

fmt.Println(m["three"]) // Output 0

where 0 is of type int of zero value.

It is worth noting that in Golang, Map is a concurrency-safe data structure, so elements in Map can be accessed and modified safely in multiple goroutines. However, simultaneous read and write operations on the same key may cause a race condition. Therefore, when performing concurrent operations, we need to use the corresponding functions provided in the sync package to ensure the security of the Map.

In short, Map in Golang is a powerful data structure that provides many convenient operations. We can initialize the Map using the make function and add new elements to the Map through the subscript operator. Maps are very efficient when accessing elements and are also very safe in multi-threaded applications.

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