如何从Python函数返回多个变量

Question

I am new to Python and trying to experiment by creating an address book. I suspect I have a problem with the displayPerson function. Can I not return multiple variables at the same time?

def lowercasewrapper(func):
    def wrapper(*args, **kwargs):
        return func(*args, **kwargs).lower()
    return wrapper

#Class with object attributes
class People():
    numofpeeps = 0
    listofpeeps = []
    def __init__(self, name, age, phone, fblink):
        self.name=name
        self.age=age
        self.phone=phone
        self.fblink=fblink
        People.numofpeeps += 1
        People.listofpeeps.append(self.age)

    @lowercasewrapper #calling the wrapper, to make all strings lowercase
    def displayPerson(self): 
        return self.name, self.age, self.phone, self.fblink

george=People("gEORge", "5", "503-405-4021", "http://facebook.com/boobs")
dave=People("dave", "10", "971-863-3905", "http://boobs.com")
charlie=People("CHARLIE", "19", "823-405-2942", "http://boobs.com")

print george.displayPerson()
print "Total number of people: ", People.numofpeeps
print "List of ages: ", People.listofpeeps


error shows the following: File "example.py", line 54, in <module>
    print george.displayPerson()
  File "example.py", line 31, in wrapper
    return func(*args, **kwargs).lower()
AttributeError: 'tuple' object has no attribute 'lower'

Answer 1

Just

def myFunc():
    return 1, 2

and in caller

var1, var2 = yourFunc()

Answer 2

Exception is raised by the lowercasewrapper not the displayPerson . You can use this instead:

def lowercasewrapper(func):
    def wrapper(*args, **kwargs):
        return [x.lower() for x in func(*args, **kwargs)]
    return wrapper

Read @DonaldMiner answer for a better explanation.

Answer 3

In this line:

    return func(*args, **kwargs).lower()

You are taking the return of that and calling it lower. When you do:

    return self.name, self.age, self.phone, self.fblink

What that really does is packs those 4 variables into a tuple, and then returns that.

So, unfortunately you are trying to call .lower() on a tuple, not on each item. Instead, you want to go through and call .lower() on everything inside:

def lowercasewrapper(func):
    def wrapper(*args, **kwargs):

        return tuple(item.lower() for item in func(*args, **kwargs))
    return wrapper

This uses a list comrpehension. If you haven't seen that syntax yet, you might want to use a for-loop to iterate over each item and lower case it.

Answer 4

Sure, you can return multiple values from a function. That's not your problem.

When you return multiple values from a function, Python automatically wraps them up in a tuple. So when you call displayPerson , it returns a tuple containing the person's name, age, phone number and facebook link in that order.

Now, in your lowercase wrapper you take the result from calling displayPerson , and call the lower method on it. Unfortunately, tuples don't have a lower method.

Instead, you'll need to return a new tuple with each of the elements individually converted to lower case:

def lowercasewrapper(func):
    def wrapper(*args, **kwargs):
        # Get initial result of your function.
        initial_tuple = func(*args, **kwargs)
        # Create a new tuple consisting of each member of the
        # initial tuple, converted to lower case.
        new_tuple = tuple([x.lower() for x in initial_tuple])
        return new_tuple
    return wrapper

Note: this could be done in a single line, I used a couple here to illustrate what's going on.