Supercharge Your Code with Python Rtype

Python has its own data types, such as integers and floating-point numbers. It also has its own list type, which can be used to store sequences of values. The main goal of Python is to make software development faster than other programming languages by minimizing the amount of code needed to perform any particular task or function. In this article, we will discuss a few things related to Python RType Notation which can be used with Python programs or script files.

What is rtype python?

rtype or return type in Python implies the data type of the return variable. For example, it can be int or float. Python has several different notations for typing and making constants. RType is one of them, but it’s not the only one. The Python documentation is a great resource for learning about these different notations and how they’re used.

Python has several different notations for typing and making constants. RType is one of them, but it’s not the only one. The Python documentation is a great resource for learning about these different notations and how they’re used.

The origination of Rtype

rtype was introduced in Python 3.7 version. It means type hinting also.

The origination of rtype in Python is when a variable or constant is created and assigned a value simultaneously. This means that if you have a rtype, it will be set automatically to the value you give it. For example, if you have a rtype named, then when you assign a value to it (like x), it will be set to x. If you try to print out fred after assigning it, then nothing will happen because it’s already been set to whatever you gave it when you created it.

Syntax of rtype

In Python, the rtype keyword is used to mark a type. The notation for rtype in Python is –


The syntax for this is:

rtype(name) = expression

Where name is any string and expression is any expression.

Usage of rtype

To specify the return type in Python, use the arrow symbol. It is entirely optional.

def add(no) -> int: #after arrow type the return type 
       return 2 + no

Otherwise, you can specify the type of the argument also.

def add(no: int) -> int:
      return no+ 2

rtype for multiple values

It might be possible that a function is returning different data types. To specify the return type, you can use ‘or’ as a connector.

:rtype: dict or list

Else, the same job is done by ‘|.’

:rtype: dict | list

To know more about syntax errors, check out this blog: Say Goodbye to Syntax Errors: The Ultimate Guide to Python Syntax Checkers(Opens in a new browser tab)

python rtype as a tuple

If the return type needs to be in the form of a tuple or you wish to have your function output as a tuple, this piece of code can be utilized.

(<type_1>, <type_2>, <type_3>, e t.c.)
#() indicates presence of tuple 

As an example, you can take this:

:rtype: (int, string, string)

Union with rtype

The union keyword can be used if you want multiple return types in one statement. This way, the redundancy factor while implementing rtype will reduce. The following example demonstrates how you can use rtype in this case:

:rtype: Union[collections.defaultdict,list]

Learn about Union of lists too in this article: Union of Two or more lists in Python(Opens in a new browser tab)

use rtype in docstrings

rtype is widely used in docstrings to demonstrate the return type. For example, if the return type is of a type generator, you may use rtype in the given way. It can belong to collections. Iterable type too.

:rtype: collections.Iterable[int]

As another example, if the function returns a list type, use rtype in the given way:

:rtype: list[float]

In the above example, the list, on being iterated, had float elements. So the brackets specify float.

rtype with pylint

With pylint, you need to use the ‘~’ symbol while specifying a class as a return type with the rtype keyword.

:rtype: ~class_name

You will get a message implying multiple returns if you have used many rtypes with pylint. So check for the rtype statements.

#remove multiple rtype 

rtype work with Sphinx

In Sphinx, we don’t prefer the usage of rtype. It is thought of as a redundant approach. Its use in Sphinx is similar to the way it is usually utilized.

rtype: Return type

Advantages of using python rtype

When you specify the return type of a function, it’s like giving the compiler permission to check whether that function is returning the right thing.

In Python, you can use this feature to ensure that your functions return what you expect. For example, if you have a function called search() and you want to make sure that it returns a list of strings, then you’ll need to specify this before calling search(). If you don’t do this, then search() might return something else instead of a list. For example, it may return an int or even None. This will probably be fine for most uses, but is your function supposed to return different types of data depending on what type of list is returned? Then it won’t work!

Specifying return types allows the compiler to check for errors before they happen. It also makes it easier for people reading your code later on because they don’t have to worry about remembering which types are allowed where. The return type of a function tells the caller what type of data can be returned when a function is called. Hence rtype in docstrings should definitely be used.


Is mentioning a rtype mandatory in Python?

Python supports dynamic allocation of space. Hence, rtype is totally optional.


Through this blog, you must have learned the implementation of rtype in Python, i.e., its usage typically and with multiple return types.

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