Odtnhj

I am new in python and I was trying to understand how does self work. As I came from JavaScript I think its bit similar to this. If I am wrong please correct me. In the meantime I wrote this code:

class Restaurant(object):
 bankrupt = False

 def open_branch(self):
 if not self.bankrupt:
 print("branch opened")

x = Restaurant()
y = Restaurant()
y.bankrupt = True

print(y.open_branch())

print(x.open_branch())

and got the output:

None
branch opened
None

As I called the open_branch() twice. It should not print thrice. I think it should print,

branch opened // for first call
None // for 2nd call

you could paste the code here and see
Please somebody explain this.

Ok, you have the following code:

class Restaurant(object):
 bankrupt = False

 def open_branch(self):
 if not self.bankrupt:
 print("branch opened")

x = Restaurant()
y = Restaurant()

till here you have two objects of type 'Restaurant'.

y.bankrupt = True

Here you changed the attribute bankrupt of the object stored in the variable y

print(y.open_branch())

This will output

None

only; why? Well first of all you are calling the function y.open_branch() but this function will not output anything because the attribute bankrupt is true so if not self.bankrupt is evaluated to false and thus the print statement is not executed. However the function open_branch() is also not returning anything (there is no return true statement or so. So print(y.open_branch()) is equal to print(None) which will output None. Next

print(x.open_branch())

For x the attribut bankrupt is false, so if not self.bankrupt is true and the print statement print("branch opened") will get evaluated. Afterwards None will be outputted for the same reason as why Nonegot outputted by print(y.open_branch()).

The two print statements at the end are only printing the returned results of the method:

print(y.open_branch())
print(x.open_branch())

Since python returns None by default if you don't explicitly specify a return statement, and you are calling the methods twice, then it's expected that you see two None statements.

If you call the method without print, you will see a single printed message.

y.open_branch()
x.open_branch()

You could improve your code by adding return statements within the method and doing the print outside, as you are doing right now. Something like

class Restaurant(object):
 bankrupt = False

 def open_branch(self):
 if not self.bankrupt:
 return "branch opened"
 return "branch closed"


x = Restaurant()
y = Restaurant() 

y.bankrupt = True

print(y.open_branch())
# output:'branch closed'

print(x.open_branch())
# output: 'branch opened'

What you're doing is you're calling print on the return value of open_branch.

So when you see it print None, you're seeing the outcome of print(x.open_branch() and print(y.open_branch().

When you see branch opened, that's the result of the print inside open_branch.

Try this:

class Restaurant(object):
 bankrupt = False

 def open_branch(self):
 result = ""
 if self.bankrupt:
 result = "Restaurant is bankrupt"
 else:
 result = "Branch opened"
 return result

x = Restaurant()
y = Restaurant()
y.bankrupt = True

print(y.open_branch())
print(x.open_branch())

There are a few things that are giving you issues here:

• 
  

  Your open_branch function isn't returning anything, so when you call print(self.open_branch(x)) it's printing None, which is what all functions in Python return by default if there is no return statement. You can solve this issue by replacing

  
  
  

  if not self.bankrupt:
   print("branch opened")
  

  
  
  

  with

  
  
  

  if not self.bankrupt:
   return "branch opened"
  

  
  



• You're calling print three times, which is why you're getting three lines printed on the console (although this will resolve itself if you replace the print in the function with the return statement I detailed above).



• 
  

  You should put an else statement under your if clause, so that it will return something useful (instead of None if self.bankrupt == True) and you can tell if the branch was opened or not. I'd suggest something like:

  
  
  

  if not self.bankrupt:
   return "branch opened"
  else:
   return "Restaurant is bankrupt, branch could not be opened"