What is hash function in python

Python hash() Method – [With Examples]

In the tutorial we will learn about the Python hash() method and its uses with examples.

What is Python hash() method?

The hash() method in python will return the hash value of a specified object if it has one. It is used to encode the data into an unrecognizable integer value.

The syntax of the hash() method is

Python hash() method Parameters

hash() method takes only one parameter:

Let’s check some examples of the hash() method in python.

Example 1: How to use the hash() method in python?

The output will be as follow:

We can only use the hash() method to return hashed values only for immutable objects. We cannot use a mutable object like a list and dictionary, but we can use a tuple as an immutable object in python.

Example 2: How to use a hash() method with python tuple?

The output will be as follow:

Let’s see what will happen when we use mutable objects with a hash() method.

Example 3: Mutable object with the hash() method.

We can see that it has raised an error “unhashable type” because we cannot hash mutable objects.

Rules of hash() method

• The hash() method will only return the hash value of an object if it has one.
• The hash() method will only work on immutable objects(integer, string float, tuple)

FAQs

How do you write a hash in Python?

The python hash function or method can be written using hash() keywords and inside the brackets, we have to add a variable or an object to get the result.

How do you write a hash function?

The hash function in python can be written using hash(), and we and use any variable, object, string or other readable python objects with the hash function.

What does hash() do in Python?

The hash() will return a hashed or encoded value of the given object.

What is syntax of hash in Python?

We can use hash(object name) as the syntax of hash in python.

What does hash do in python?

The hash() method will encode the given object and return the hashed format of that object.

How to use hash in python?

It is very easy to use the python hash() method, we just need to call the hash() method with an object as the parameter.

what is hash function in python?

The hash function is a built-in python function that is used to encode the object in a hashed format.

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hash() in Python

Hashing means using some function or algorithm to map object data to some representative value. Hashing is designed to solve the problem of needing to efficiently find or store an item in a collection. It is a technique to make things more efficient by effectively narrowing down the search. Generally, some hash codes are used to generate an index, at which the value is stored.

The concept of Hashing exists with a Hash table. In Hash tables, you store data in form of key and value pairs where the key is the input for which its corresponding value is obtained. If you know a little bit of Python, the first thing that might come to your mind is a Dictionary.

The process of Hashing involves converting a given key into another value. A Hash function is used to generate the new value according to a mathematical algorithm. The result of a Hash function is known as a Hash value or simply, a Hash.

What is hash() in Python?

hash() in Python is a built-in function that is used to return the Hash value of a given object. Hash values are integers that are useful when comparing the Dictionary keys during Dictionary look-up that is searching for the value of a given key in the Dictionary. hash() function works only for immutable objects. Let’s quickly go through what does this mean.

Hashable Objects in Python

A very simplified definition of Hash: A fixed size integer that is computed using the data stored in the object. In Python, an immutable object (that cannot be modified once created) is Hashable, meaning its value does not change during its lifetime. This allows Python to create a unique hash value to identify it. Now we can understand, why the keys in Dictionary are always immutable simply because their Hash values are compared and they need to be unique.

Immutable data types in Python come with a built-in method for computing their Hash value, which is hash() . The hash() function internally called the special method which is __hash__() .

Syntax of hash()

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hash() in Python

hash() function in python is used to return a hashed integer value of the object we pass as a parameter into it iff the object is hashable. Generally, the hash values are used to compare the dictionary keys while doing a dictionary lookup.

Syntax of hash() function in Python

Syntax for using the hash() function is as follows:

Parameters of hash() function in Python

hash() function takes one parameter as an input:

• object : an object whose hash value is to be returned. An object can be an integer, string, list, tuple, etc.

Return Values of hash() function in Python

• hash() function returns an integer value which is the hash of the object passed into the function.

Example of hash() function in Python

What is hash() function in Python?

hash() function is used in Python to obtain the object’s hash value. The object can be of integer , string , list , tuple type. The integer value is returned from the hash function, which is the hashed value of the object. The hashed values are generally used for the faster comparison between the two objects as the hash values are directly compared rather than comparing each object’s value.

How does hash() work on custom objects?

_hash_() method is called internally while we use the hash() function in python. So in order to override the _hash_() method we need to have our own custom definition of _eq_() and _hash_() functions. Below is the example where we can see how we can use the hash() function on custom objects.

More Examples

Example 1: Using hash() with integer, string and float

Explanation:

As we said, applying the hash() function on integer, string, and float values will fetch the integer value as output, which are the hash values of the original inputs.

Example 2: Using hash() with immutable tuple objects

Explanation:

On applying the hash() function on an immutable object, we get the integer value which is the hash value of the entire set.

Example 3: Using hash() with the mutable object

Explanation: On applying the hash() function on mutable objects an error is raised saying unhashable type as the list is a mutable object which cannot be hashed using the hash function.

Conclusion

• hash() function is used to fetch the hash values of the python objects.
• hash() function returns the integer value if the hashable object passed in the function as a parameter.
• hash() function calls inbuilt __hash__() function which can be overriden for hashing the custom objects.
• hash() function can be applied to immutable objects.
• hash() function cannot be applied to mutable objects.

See Also

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