Check if one of all variables is empty

Question

def ask():
    global name, loca

    print "What's your name?"
    name = raw_input('> ')
    print "Where are you from?"
    loca = raw_input('> ')

    if name or loca == None:
        print "Please enter valid details."
        ask()

ask()
print "Alright, so you're " + name + ", from " + loca + "."

With this script, it will only ever print the last line if both of my variables are empty. If I fill in one, or both, it triggers that if, making me redo the function.

What am I doing wrong here?

Solution 1

You have very well isolated the problem:

if name or loca == None:

Here you think it says:

"If either name or loca equal none:"

But instead it says:

"if (name) is true or (loca equals None) is true:"

Where it should say:

"if (name equals none) is true or (loca equals none) is true:"

Which is:

if name is None or loca is None:

See, by the way, that None comparisons are better carried out with is, since there is only one None object.

Also, a more pythonic way of doing it is:

if not all((name, loca)):

Or, seeing as "all" it's just 2 variables:

if not (name and loca):

If you don't understand, read around a bit (the Python tutorial is excellent -- go for the conditionals part). Good luck!

Solution 2

try this

if not all([name, loca]):
   print "Please enter valid details"
   ask()

Solution 3

Well, neither name nor loca can ever be None after running ask(). At worst they're empty strings: ''. What you're doing is asking if name is True, which it is if name has any value other than ''.

What you want to do is check if the names have a non-empty value:

if not (name and loca):
    …

should be fine.

Solution 4

if name or loca == None:

This will never trigger for two reasons:

1. First, if you don't enter any data, you get an empty string, not None, so loca == None will never be true.

2. Second, your if statement is checking two things: whether name is truthy (contains any data), and whether loca == None. You probably meant if name == None or loca == None.

Combining these two things, you can write:

if name == "" or loca == "":

Or, simplifying and taking advantage of the fact that strings are "truthy" if they contain data:

if not (name and loca):

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