Trouble understanding the difference between passing result to another function and retuning result to...











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I've written a script in python using two functions within it. The first function is supposed to get some links from a webpage and the other should print it in the console.



My question is what difference does it make when I pass the result from one function to another function using return keyword like return get_info(elem)? Usually doing only this get_info(elem), I can pass stuffs from one function to another then when to choose this return get_info(elem) and why?



An example might be:



import requests
from bs4 import BeautifulSoup

def get_links(url):
response = requests.get(url)
soup = BeautifulSoup(response.text,"lxml")
elem = soup.select_one(".info h2 a[data-analytics]").get("href")
get_info(elem) #why this one
return get_info(elem) #or why this

def get_info(link):
print(link)









share|improve this question






















  • It sounds like you might be thinking of languages like Ruby which has implicit returns. Python doesn't have those and neither do most languages.
    – pguardiario
    Nov 22 at 6:23















up vote
2
down vote

favorite












I've written a script in python using two functions within it. The first function is supposed to get some links from a webpage and the other should print it in the console.



My question is what difference does it make when I pass the result from one function to another function using return keyword like return get_info(elem)? Usually doing only this get_info(elem), I can pass stuffs from one function to another then when to choose this return get_info(elem) and why?



An example might be:



import requests
from bs4 import BeautifulSoup

def get_links(url):
response = requests.get(url)
soup = BeautifulSoup(response.text,"lxml")
elem = soup.select_one(".info h2 a[data-analytics]").get("href")
get_info(elem) #why this one
return get_info(elem) #or why this

def get_info(link):
print(link)









share|improve this question






















  • It sounds like you might be thinking of languages like Ruby which has implicit returns. Python doesn't have those and neither do most languages.
    – pguardiario
    Nov 22 at 6:23













up vote
2
down vote

favorite









up vote
2
down vote

favorite











I've written a script in python using two functions within it. The first function is supposed to get some links from a webpage and the other should print it in the console.



My question is what difference does it make when I pass the result from one function to another function using return keyword like return get_info(elem)? Usually doing only this get_info(elem), I can pass stuffs from one function to another then when to choose this return get_info(elem) and why?



An example might be:



import requests
from bs4 import BeautifulSoup

def get_links(url):
response = requests.get(url)
soup = BeautifulSoup(response.text,"lxml")
elem = soup.select_one(".info h2 a[data-analytics]").get("href")
get_info(elem) #why this one
return get_info(elem) #or why this

def get_info(link):
print(link)









share|improve this question













I've written a script in python using two functions within it. The first function is supposed to get some links from a webpage and the other should print it in the console.



My question is what difference does it make when I pass the result from one function to another function using return keyword like return get_info(elem)? Usually doing only this get_info(elem), I can pass stuffs from one function to another then when to choose this return get_info(elem) and why?



An example might be:



import requests
from bs4 import BeautifulSoup

def get_links(url):
response = requests.get(url)
soup = BeautifulSoup(response.text,"lxml")
elem = soup.select_one(".info h2 a[data-analytics]").get("href")
get_info(elem) #why this one
return get_info(elem) #or why this

def get_info(link):
print(link)






python python-3.x function web-scraping return






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Nov 22 at 5:04









robots.txt

19311




19311












  • It sounds like you might be thinking of languages like Ruby which has implicit returns. Python doesn't have those and neither do most languages.
    – pguardiario
    Nov 22 at 6:23


















  • It sounds like you might be thinking of languages like Ruby which has implicit returns. Python doesn't have those and neither do most languages.
    – pguardiario
    Nov 22 at 6:23
















It sounds like you might be thinking of languages like Ruby which has implicit returns. Python doesn't have those and neither do most languages.
– pguardiario
Nov 22 at 6:23




It sounds like you might be thinking of languages like Ruby which has implicit returns. Python doesn't have those and neither do most languages.
– pguardiario
Nov 22 at 6:23












2 Answers
2






active

oldest

votes

















up vote
1
down vote



accepted










Let us first simplify your function so that you can run it and compare the results:



def get_links(url):
url = "this returns link: {}".format(url)
get_info(url) #why this one
return get_info(url) #or why this

def get_info(link):
print(link)

get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com


Your function now returns print twice. First when you called the function, and second when you returned the function, and in this case actually returns None because get_info does not return anything.



This is evident here:



url = get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com

url
>> *nothing happens*


The results of return are more apparent if it actually does something, for example:



def get_links(url):
url = "this returns link: {}".format(url)
return get_info(url)

def get_info(link):
return "get_info does something, {}".format(link)

url = get_links('google.com')
url

>>'get_info does something, this returns link: google.com'


If you do not use return, it just means the function will not return anything, which happens for example if you just want to print the results as you did. You can further try this out by assigning a name like I did above to a function does has no return and the result will essentially be None.






share|improve this answer





















  • I don't think he's calling the function twice. He's just asking what the difference is between calling it with or without return.
    – Barmar
    Nov 22 at 5:37












  • I just meant to illustrate that the 2 calls in get_links call get_info twice, one with return and one without does not return any value even when assigned to a variable because it is probably different than the way he intended it to work.
    – BernardL
    Nov 22 at 5:43










  • Read the comments in the code, it says "why this ... or this". He wants to know why he should use one or the other.
    – Barmar
    Nov 22 at 6:00










  • Perhaps. Why was too broad for me to answer and therefore I replied with an explanation of what it does.
    – BernardL
    Nov 22 at 6:10










  • If you haven't come across this post already, please take a look @BernardL.
    – robots.txt
    Nov 22 at 16:48




















up vote
1
down vote













return get_info(elem)


will call the get_info() function, then take whatever it returned, and return that same value from get_links(). It's roughly equivalent to:



temp = get_info(elem)
return temp


But since get_info() doesn't return anything, it just prints the link, there's not much point in using it in a return statement. Writing just



get_info(elem)


calls the function without doing anything with its return value (if it returned anything).






share|improve this answer





















  • I can see a huge difference between them when I go through this script. The script in the answer has got this return get_data(itemlink['href']) without which I don't get any result. I meant I don't get any result when I do get_data(itemlink['href']).
    – robots.txt
    Nov 22 at 5:16










  • get_data doesn't return anything, it just prints, like the get_info function here.
    – Barmar
    Nov 22 at 5:37











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
1
down vote



accepted










Let us first simplify your function so that you can run it and compare the results:



def get_links(url):
url = "this returns link: {}".format(url)
get_info(url) #why this one
return get_info(url) #or why this

def get_info(link):
print(link)

get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com


Your function now returns print twice. First when you called the function, and second when you returned the function, and in this case actually returns None because get_info does not return anything.



This is evident here:



url = get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com

url
>> *nothing happens*


The results of return are more apparent if it actually does something, for example:



def get_links(url):
url = "this returns link: {}".format(url)
return get_info(url)

def get_info(link):
return "get_info does something, {}".format(link)

url = get_links('google.com')
url

>>'get_info does something, this returns link: google.com'


If you do not use return, it just means the function will not return anything, which happens for example if you just want to print the results as you did. You can further try this out by assigning a name like I did above to a function does has no return and the result will essentially be None.






share|improve this answer





















  • I don't think he's calling the function twice. He's just asking what the difference is between calling it with or without return.
    – Barmar
    Nov 22 at 5:37












  • I just meant to illustrate that the 2 calls in get_links call get_info twice, one with return and one without does not return any value even when assigned to a variable because it is probably different than the way he intended it to work.
    – BernardL
    Nov 22 at 5:43










  • Read the comments in the code, it says "why this ... or this". He wants to know why he should use one or the other.
    – Barmar
    Nov 22 at 6:00










  • Perhaps. Why was too broad for me to answer and therefore I replied with an explanation of what it does.
    – BernardL
    Nov 22 at 6:10










  • If you haven't come across this post already, please take a look @BernardL.
    – robots.txt
    Nov 22 at 16:48

















up vote
1
down vote



accepted










Let us first simplify your function so that you can run it and compare the results:



def get_links(url):
url = "this returns link: {}".format(url)
get_info(url) #why this one
return get_info(url) #or why this

def get_info(link):
print(link)

get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com


Your function now returns print twice. First when you called the function, and second when you returned the function, and in this case actually returns None because get_info does not return anything.



This is evident here:



url = get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com

url
>> *nothing happens*


The results of return are more apparent if it actually does something, for example:



def get_links(url):
url = "this returns link: {}".format(url)
return get_info(url)

def get_info(link):
return "get_info does something, {}".format(link)

url = get_links('google.com')
url

>>'get_info does something, this returns link: google.com'


If you do not use return, it just means the function will not return anything, which happens for example if you just want to print the results as you did. You can further try this out by assigning a name like I did above to a function does has no return and the result will essentially be None.






share|improve this answer





















  • I don't think he's calling the function twice. He's just asking what the difference is between calling it with or without return.
    – Barmar
    Nov 22 at 5:37












  • I just meant to illustrate that the 2 calls in get_links call get_info twice, one with return and one without does not return any value even when assigned to a variable because it is probably different than the way he intended it to work.
    – BernardL
    Nov 22 at 5:43










  • Read the comments in the code, it says "why this ... or this". He wants to know why he should use one or the other.
    – Barmar
    Nov 22 at 6:00










  • Perhaps. Why was too broad for me to answer and therefore I replied with an explanation of what it does.
    – BernardL
    Nov 22 at 6:10










  • If you haven't come across this post already, please take a look @BernardL.
    – robots.txt
    Nov 22 at 16:48















up vote
1
down vote



accepted







up vote
1
down vote



accepted






Let us first simplify your function so that you can run it and compare the results:



def get_links(url):
url = "this returns link: {}".format(url)
get_info(url) #why this one
return get_info(url) #or why this

def get_info(link):
print(link)

get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com


Your function now returns print twice. First when you called the function, and second when you returned the function, and in this case actually returns None because get_info does not return anything.



This is evident here:



url = get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com

url
>> *nothing happens*


The results of return are more apparent if it actually does something, for example:



def get_links(url):
url = "this returns link: {}".format(url)
return get_info(url)

def get_info(link):
return "get_info does something, {}".format(link)

url = get_links('google.com')
url

>>'get_info does something, this returns link: google.com'


If you do not use return, it just means the function will not return anything, which happens for example if you just want to print the results as you did. You can further try this out by assigning a name like I did above to a function does has no return and the result will essentially be None.






share|improve this answer












Let us first simplify your function so that you can run it and compare the results:



def get_links(url):
url = "this returns link: {}".format(url)
get_info(url) #why this one
return get_info(url) #or why this

def get_info(link):
print(link)

get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com


Your function now returns print twice. First when you called the function, and second when you returned the function, and in this case actually returns None because get_info does not return anything.



This is evident here:



url = get_links('google.com')
>>this returns link: google.com
>>this returns link: google.com

url
>> *nothing happens*


The results of return are more apparent if it actually does something, for example:



def get_links(url):
url = "this returns link: {}".format(url)
return get_info(url)

def get_info(link):
return "get_info does something, {}".format(link)

url = get_links('google.com')
url

>>'get_info does something, this returns link: google.com'


If you do not use return, it just means the function will not return anything, which happens for example if you just want to print the results as you did. You can further try this out by assigning a name like I did above to a function does has no return and the result will essentially be None.







share|improve this answer












share|improve this answer



share|improve this answer










answered Nov 22 at 5:23









BernardL

2,3331829




2,3331829












  • I don't think he's calling the function twice. He's just asking what the difference is between calling it with or without return.
    – Barmar
    Nov 22 at 5:37












  • I just meant to illustrate that the 2 calls in get_links call get_info twice, one with return and one without does not return any value even when assigned to a variable because it is probably different than the way he intended it to work.
    – BernardL
    Nov 22 at 5:43










  • Read the comments in the code, it says "why this ... or this". He wants to know why he should use one or the other.
    – Barmar
    Nov 22 at 6:00










  • Perhaps. Why was too broad for me to answer and therefore I replied with an explanation of what it does.
    – BernardL
    Nov 22 at 6:10










  • If you haven't come across this post already, please take a look @BernardL.
    – robots.txt
    Nov 22 at 16:48




















  • I don't think he's calling the function twice. He's just asking what the difference is between calling it with or without return.
    – Barmar
    Nov 22 at 5:37












  • I just meant to illustrate that the 2 calls in get_links call get_info twice, one with return and one without does not return any value even when assigned to a variable because it is probably different than the way he intended it to work.
    – BernardL
    Nov 22 at 5:43










  • Read the comments in the code, it says "why this ... or this". He wants to know why he should use one or the other.
    – Barmar
    Nov 22 at 6:00










  • Perhaps. Why was too broad for me to answer and therefore I replied with an explanation of what it does.
    – BernardL
    Nov 22 at 6:10










  • If you haven't come across this post already, please take a look @BernardL.
    – robots.txt
    Nov 22 at 16:48


















I don't think he's calling the function twice. He's just asking what the difference is between calling it with or without return.
– Barmar
Nov 22 at 5:37






I don't think he's calling the function twice. He's just asking what the difference is between calling it with or without return.
– Barmar
Nov 22 at 5:37














I just meant to illustrate that the 2 calls in get_links call get_info twice, one with return and one without does not return any value even when assigned to a variable because it is probably different than the way he intended it to work.
– BernardL
Nov 22 at 5:43




I just meant to illustrate that the 2 calls in get_links call get_info twice, one with return and one without does not return any value even when assigned to a variable because it is probably different than the way he intended it to work.
– BernardL
Nov 22 at 5:43












Read the comments in the code, it says "why this ... or this". He wants to know why he should use one or the other.
– Barmar
Nov 22 at 6:00




Read the comments in the code, it says "why this ... or this". He wants to know why he should use one or the other.
– Barmar
Nov 22 at 6:00












Perhaps. Why was too broad for me to answer and therefore I replied with an explanation of what it does.
– BernardL
Nov 22 at 6:10




Perhaps. Why was too broad for me to answer and therefore I replied with an explanation of what it does.
– BernardL
Nov 22 at 6:10












If you haven't come across this post already, please take a look @BernardL.
– robots.txt
Nov 22 at 16:48






If you haven't come across this post already, please take a look @BernardL.
– robots.txt
Nov 22 at 16:48














up vote
1
down vote













return get_info(elem)


will call the get_info() function, then take whatever it returned, and return that same value from get_links(). It's roughly equivalent to:



temp = get_info(elem)
return temp


But since get_info() doesn't return anything, it just prints the link, there's not much point in using it in a return statement. Writing just



get_info(elem)


calls the function without doing anything with its return value (if it returned anything).






share|improve this answer





















  • I can see a huge difference between them when I go through this script. The script in the answer has got this return get_data(itemlink['href']) without which I don't get any result. I meant I don't get any result when I do get_data(itemlink['href']).
    – robots.txt
    Nov 22 at 5:16










  • get_data doesn't return anything, it just prints, like the get_info function here.
    – Barmar
    Nov 22 at 5:37















up vote
1
down vote













return get_info(elem)


will call the get_info() function, then take whatever it returned, and return that same value from get_links(). It's roughly equivalent to:



temp = get_info(elem)
return temp


But since get_info() doesn't return anything, it just prints the link, there's not much point in using it in a return statement. Writing just



get_info(elem)


calls the function without doing anything with its return value (if it returned anything).






share|improve this answer





















  • I can see a huge difference between them when I go through this script. The script in the answer has got this return get_data(itemlink['href']) without which I don't get any result. I meant I don't get any result when I do get_data(itemlink['href']).
    – robots.txt
    Nov 22 at 5:16










  • get_data doesn't return anything, it just prints, like the get_info function here.
    – Barmar
    Nov 22 at 5:37













up vote
1
down vote










up vote
1
down vote









return get_info(elem)


will call the get_info() function, then take whatever it returned, and return that same value from get_links(). It's roughly equivalent to:



temp = get_info(elem)
return temp


But since get_info() doesn't return anything, it just prints the link, there's not much point in using it in a return statement. Writing just



get_info(elem)


calls the function without doing anything with its return value (if it returned anything).






share|improve this answer












return get_info(elem)


will call the get_info() function, then take whatever it returned, and return that same value from get_links(). It's roughly equivalent to:



temp = get_info(elem)
return temp


But since get_info() doesn't return anything, it just prints the link, there's not much point in using it in a return statement. Writing just



get_info(elem)


calls the function without doing anything with its return value (if it returned anything).







share|improve this answer












share|improve this answer



share|improve this answer










answered Nov 22 at 5:09









Barmar

417k34240341




417k34240341












  • I can see a huge difference between them when I go through this script. The script in the answer has got this return get_data(itemlink['href']) without which I don't get any result. I meant I don't get any result when I do get_data(itemlink['href']).
    – robots.txt
    Nov 22 at 5:16










  • get_data doesn't return anything, it just prints, like the get_info function here.
    – Barmar
    Nov 22 at 5:37


















  • I can see a huge difference between them when I go through this script. The script in the answer has got this return get_data(itemlink['href']) without which I don't get any result. I meant I don't get any result when I do get_data(itemlink['href']).
    – robots.txt
    Nov 22 at 5:16










  • get_data doesn't return anything, it just prints, like the get_info function here.
    – Barmar
    Nov 22 at 5:37
















I can see a huge difference between them when I go through this script. The script in the answer has got this return get_data(itemlink['href']) without which I don't get any result. I meant I don't get any result when I do get_data(itemlink['href']).
– robots.txt
Nov 22 at 5:16




I can see a huge difference between them when I go through this script. The script in the answer has got this return get_data(itemlink['href']) without which I don't get any result. I meant I don't get any result when I do get_data(itemlink['href']).
– robots.txt
Nov 22 at 5:16












get_data doesn't return anything, it just prints, like the get_info function here.
– Barmar
Nov 22 at 5:37




get_data doesn't return anything, it just prints, like the get_info function here.
– Barmar
Nov 22 at 5:37


















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