How to prevent Python function from returning None

Question

I am parsing HTML table with BeautifulSoup like this:

for tr in table_body.find_all('tr'):      
            for td in tr:  
                if td.text == 'Description':
                    description = td.find_next('td').text
                if td.text == 'Category':
                    category = td.find_next('td').text                             
                if td.text == 'Department':
                    department = td.find_next('td').text                             
                if td.text == 'Justification':
                    justification = td.find_next('td').text
print(description, category, department, justification)

I refactored the multiple if statements into a function:

def html_check(td, text):
        if td.text == text:
            value = td.find_next('td').text
            return value

that is called like this:

for tr in table_body.find_all('tr'):      
            for td in tr:  
                description= html_check(td, 'Description')
                category = html_check(td, 'Category')
                department = html_check(td, 'Department')
                justification = html_check(td, 'Justification')
print(description, category, department, justification)

My problem is that when the function html_check will not find a match, it will return None, which will be printed. This is not desirable.

Is there any way to make this function return a value only when the if condition in it is met?

What should happen when the condition is not met? Return an empty string? If so - just add `return ""` at the end of your function, outside of the `if` condition. If you don't return anything from your function explicitly, `None` will be returned. — zwer, Jul 24 '18 at 12:20
`None` returned from a function isn't automatically printed. Just use another `if` check to see if the function returns `None` and only `print()` when it returns something other than `None`. — roganjosh, Jul 24 '18 at 12:22
"Is there any way to make this function return a value only when the if condition in it is met?" No. Python will have the function return `None` if you don't specify a return value for the given input. — John Coleman, Jul 24 '18 at 12:23
When the condition is not met, I want the function to behave alsmost like it was never called - so to return nothing, not even `None` — barciewicz, Jul 24 '18 at 12:23
Python doesn't work like that. You can *ignore* the `None`, but you can't prevent the interpreter from returning it. Just call the function conditionally. — John Coleman, Jul 24 '18 at 12:24

Christian W. · Accepted Answer · 2018-07-24T12:38:58.393

Python will always return None, if no return is specified at the point of exiting the function call. Your options are:

return something else if the condition is not met.
ignore the function if it returns None

option 1 (return something else when the condition isn't met):

 def html_check(td, text):
     if td.text == text:
        value = td.find_next('td').text
        return value
     return "no value found"

option 2 (ignores the function if None is returned):

if html_check(td, 'section'):
     # do things

score 2 · Answer 2 · answered Jul 24 '18 at 12:26

You can specify a default value, to return, in case no element matches. Something like:

def html_check(td, text):
        if td.text == text:
            value = td.find_next('td').text
            return value
        return "Default Value"

Also, you can spcify the default value via argument, which would somewhat look like :

 def html_check(td, text, default_value):
            if td.text == text:
                value = td.find_next('td').text
                return value
    return default_value

And, then use it like:

for tr in table_body.find_all('tr'):      
            for td in tr:  
                description= html_check(td, 'Description', 'Default Description')
                category = html_check(td, 'Category','Default Category')
                department = html_check(td, 'Department', 'Default Department')
                justification = html_check(td, 'Justification', 'Default Justification')
print(description, category, department, justification)

score 1 · Answer 3 · answered Jul 24 '18 at 12:36

You can try this to print only those whose values match.

for tr in table_body.find_all('tr'): 
            fields = ['Description','Category','Department','Justification']
            for td in tr:
                print (['{}:{}'.format(i,html_check(td,i)) for i in fields if html_check(td,i)])

TheExorcist · Answer 4 · 2018-07-24T12:48:16.000

0

My solution would be

def html_check(td, text):
        if td.text == text:
            value = td.find_next('td').text
            if not value is None:
               return value
            else:
                value ="Not able to find"
                return value

However we can not remove None, if html_check function is not returning anything, in python we init it with None. But for our sake we can bypass and init it with something else dev wants.

edited Jul 24 '18 at 12:48

answered Jul 24 '18 at 12:27

TheExorcist

1,966
1
19
25

Your solution, as it's currently provided, will still return `None`. You might assign `value = "Not able to find"`, but you don't return it. Which means it still returns `None` – TayTay Jul 24 '18 at 12:35
Ohh I forgot to add some line. My code is not optimized, its just an example not more than that, we can optimize the code so that return is called once. – TheExorcist Jul 24 '18 at 12:47

score 0 · Answer 5 · answered Apr 21 '22 at 04:06

0

Only print if all variables have a value:

print_me = description and category and department and justification
print(description, category, department, justification) if print_me else None

answered Apr 21 '22 at 04:06

BeRT2me

12,699
2
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31

How to prevent Python function from returning None

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