Introduction to Python functions: usage and examples of hash functions

Introduction to Python functions: Usage and examples of hash function

1. Introduction
   In Python, the hash function is a built-in function that is used to generate The hash value of the object. A hash value is the result of an algorithm that maps a binary value of arbitrary length to a unique value of fixed length. The function of the hash function is to make the values ​​well distributed and to be located quickly. In Python, the hash function can be applied to basic data types such as strings, integers, floating point numbers, etc., as well as hashable objects such as tuples and dictionaries.
2. Usage
   The usage of the hash function is very simple. You only need to call hash and pass in the object to be hashed as a parameter. The function returns an integer hash value.

For example, we can use the hash function to hash the string:

string = "Hello World"
hash_value = hash(string)
print(hash_value)

In the above code, we use the hash function to hash the string "Hello World" , and assign the result to the hash_value variable. Finally, we output the hash value via the print function.

3. Example

3.1 Hash string

string = "Hello World"
hash_value = hash(string)
print(hash_value)

Output: 2922927337147303222

In this example, we have the string " Hello World" performs a hash operation and prints out the hash value.

3.2 Hash integer

num = 12345
hash_value = hash(num)
print(hash_value)

Output: 12345

In this example, we hash the integer 12345 and print out the hash value. Since an integer is an immutable object, its hash value is equal to itself.

3.3 Hash tuple

tuple_1 = (1, 2, 3)
hash_value_1 = hash(tuple_1)

tuple_2 = (4, 5, 6)
hash_value_2 = hash(tuple_2)

print(hash_value_1)
print(hash_value_2)

Output:

• The hash value of tuple_1: 2528502973977326415
• The hash value of tuple_2: 2528502973977326683

In this example, we hash two tuples separately and print out their hash values.

3.4 Hash Dictionary

dict_1 = {"name": "Alice", "age": 18}
hash_value_1 = hash(frozenset(dict_1.items()))

dict_2 = {"name": "Bob", "age": 20}
hash_value_2 = hash(frozenset(dict_2.items()))

print(hash_value_1)
print(hash_value_2)

Output:

• Hash value of dict_1: -4894169783345032514
• Hash value of dict_2: 2528502973977326681

In this example, we hash the two dictionaries separately and print out their hash values. Since the dictionary is a mutable object, we need to convert it to an immutable frozenset object before performing a hash operation.

Summary

• The hash function can be used to generate a hash value of an object.
• The hash function is a built-in function and can be used directly.
• The hash function is suitable for basic data types and hashable objects.
• The hash values ​​of different objects are unique.

Through this article, we learned the usage and examples of hash function and understood its basic operation. In actual programming, reasonable use of hash functions can improve program performance and efficiency.

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