Return Functions –
From the above discussion you can understand that, when the function is called with parentheses, the code is executed and returns the result. And, when it is called without parentheses, a function reference is returned to the callable. So, what happens when a function is coded along with a return statement with parentheses and without parentheses. Let’s go through an example.
With Parentheses
Python3
def concatenate_string(*args): string1 = args[0] string2 = args[1] def merge_string(string1, string2): return string1 + string2 return merge_string(string1, string2)def func(): conc_obj = concatenate_string('Hello, ', 'George') print(conc_obj)func() |
Output
Hello, George
From the above example, it’s clear that the
merge_string
is a function within the function
concatenate_string
and the main function (
concatenate_string
) returns the sub-function (
merge_string
) to the caller.
return merge_string(string1, string2)
Here
merge_string
is invoked with parentheses, hence it executes and provides the result to the
concatenate_string
from where the result is passed to
func
.
Without Parentheses
Python3
def concatenate_string(): def merge_string(string1, string2): return string1 + string2 return merge_stringdef func(): # return the reference of merge_string func conc_obj = concatenate_string() print(conc_obj) # prints the reference # executes the reference print(conc_obj('Hello, ', 'George')) func() |
Output:
<function concatenate_string..merge_string at 0x7f1e54ebc158>
Hello, George
Since the
merge_string
is used without parentheses, the
concatenate_string
passes the function reference to the callable
func
rather than executing the
merge_string
.
return merge_string
Hence, we can conclude that when we code sub-function with parentheses in a return statement, the main function executes the sub-function and passes the result to the callable. And, when we code subfunction without parentheses in a return statement, the main function passes the sub-function reference to the callable rather than executing it. Here the callable decides what to do with the reference.
Python – Invoking Functions with and without Parentheses
Functions in Python are the defined blocks of code that perform a specific task. In this section, we will discuss the difference in invoking functions with and without Parentheses.
- When we call a function with parentheses, the function gets execute and returns the result to the callable.
- In another case, when we call a function without parentheses, a function reference is sent to the callable rather than executing the function itself.
Let’s discuss 3 important concepts:
- Invoking functions
- Return functions
- Passing functions