return statement usage

[SB_J]

Hello!

1)

def square(x):
    return(x*x)
print(square(4))

2)

def square(x):
    print(x*x)
square(4)

Why do I have to use a return statement(1) when I can get the output by calling the function directly(2)?

[perfringo]

Maybe you should start with question - why you need function for printing something out

Functions with no return or yield return None:

>>> def square(x):
...     print(x*x)
... 
>>> square(4)
16
>>> print(square(4))
16
None      
>>> a = square(4)
16
>>> a
>>> a is None
True

[SB_J]

Okay. Thank you :-)

[snippsat]

Why do I have to use a return statement(1) when I can get the output by calling the function directly(2)?

Functions is a first step to structure code better,one function can do a task and return data out.
Then other functions can take that data in as argument and do other task.
This make code easier to read and test(functions should be isolate from data outside) than writing all code in global namespace.

A working example of what mention over.

from bs4 import BeautifulSoup
import json
import requests

def data_from_web():
    '''Read title from web-site'''
    url = 'http://CNN.com'
    response = requests.get(url)
    soup = BeautifulSoup(response.content, 'html.parser')
    return soup.find('title').text

def process_data(data):
    '''Make dicionary'''
    modified_data = {'title': data}
    return modified_data

def write_data(data):
    '''Serializing data to disk'''
    with open('title.json', 'w') as f_out:
        json.dump(data, f_out)

def result():
    data = data_from_web()
    modified_data = process_data(data)
    write_data(modified_data)

if __name__ == "__main__":
    result()