Python: Printing the return of a function

Question

Python 2.7. The below function below returns either True or False. I'm trying to print this result. Now I know that I could just replace "return" with "print", but I don't want to print from within the function.

def OR_Gate():                                              
  a = raw_input("Input A:")                                        
  b = raw_input("Input B:")                                        
  if a == True or b == True:                                      
      return True                                                  
  if a == False and b == False:                                    
      return False

print OR_Gate()

When I run the below code, I'm prompted to enter values for a and b, and then the output is "None", as opposed to either True or False. How do I just print the return of the function OR_Gate?

Compare `a` and `b` against strings e.g. `if a == 'True' or b == 'True':` — vaultah, Dec 25 '15 at 17:40
The problem is because neither if block evaluates to True, the function reaches the end and returns `None`. — David Maust, Dec 25 '15 at 17:50

score 5 · Accepted Answer · answered Dec 25 '15 at 17:45

You are comparing booleans to strings True != "True" and False != "False" so your function returns None which is the default when you don't specify a return value. You can also simplify your code using in using "True":

def OR_Gate():                                              
  a = raw_input("Input A:")                                        
  b = raw_input("Input B:")                                        
  return "True" in [a,b]

zedfoxus · Answer 2 · 2015-12-25T18:08:15.660

Padraic has a nice answer. In addition to that, if you want to compare your raw input against a set of characters to determine truthiness, you could do something like this:

def OR_Gate():
    truevalues = ['true','t','yes','y','1']
    falsevalues = ['false','f','no','n','0']
    a = raw_input("Input A:")
    b = raw_input("Input B:")

    # if you want to have a one line return, you could do this
    # send back False if a and b are both false; otherwise send True
    # return False if a.lower() in falsevalues and b.lower() in falsevalues else True

    if a.lower() in truevalues or b.lower() in truevalues:
        return True
    if a.lower() in falsevalues or b.lower() in falsevalues:
        return False

print OR_Gate()

Some results:

$ python test.py
Input A:t
Input B:t
True

$ python test.py
Input A:f
Input B:t
True

$ python test.py
Input A:f
Input B:f
False

Some minor improvements: Instead of checking for `True` and `true`, just lowercase the input, e.g. `a.lower() in truevalues`. That way `'tRue'` is also accepted and we have to make fewer comparisons. And instead of doing `if something: return True // if (not something): return False` just do `return something`. — poke, Dec 25 '15 at 18:04

Rockybilly · Answer 3 · 2015-12-29T17:23:22.443

-1

Well I like posting interesting answers. Here comes one:

def OR_Gate():                                              
  return eval(raw_input("Input A:")) or eval(raw_input("Input B:"))

However, using eval() through user input provides a direct access to python interpeter. So if this code is part of a website project etc, you should not use this. Other than that, I think it is cool.

edited Dec 29 '15 at 17:23

answered Dec 25 '15 at 21:04

Rockybilly

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Correct condition is `a or b` – remram Dec 29 '15 at 14:43
`eval(raw_input(...))` == `input(...)` – Andrea Corbellini Dec 29 '15 at 17:27
That is correct, but I wanted to show what really was going on after using raw_input like OP used. Other than that, you are absolutely right. – Rockybilly Dec 29 '15 at 17:29

Python: Printing the return of a function

3 Answers3