列表和变量可以从函数中返回吗？

Question

I can do this..

def funcOne():
    a,b = funcTwo()
    print a, b

def funcTwo():
    .....
    ......   
    return x, y

But can a list also be returned from funcTwo and displayed in funcOne ALONG with the 2 values? Nothing seems to work

Answer 1

When you return multiple values, all you are doing is building a single tuple containing those values, and returning it. You can construct tuples with anything in it, and a list comes under anything:

def funcOne():
    a, b, some_list = funcTwo()
    print a, b, some_list

def funcTwo():
    ...
    some_list = [...] 
    return x, y, some_list

If you mean you wish to return the values from the list, you can do that by just returning the list, unpacking works with lists too:

def funcOne():
    a, b, = funcTwo()
    print a, b

def funcTwo():
    ...
    some_list = [x, y] 
    return some_list

Or if you want to extend the returned values with all the values from a list, you just need to concatenate a list of values you wish to return with the list of extra values:

def funcOne():
    a, b, c, d = funcTwo()
    print a, b, c, d

def funcTwo():
    ...
    some_list = [z, w] 
    return [x, y] + some_list

Answer 2

>>> def list_and_vars():
    a, b = "fee", "fi"
    c = ["fo", "fum"]
    return a, b, c

>>> print list_and_vars()
('fee', 'fi', ['fo', 'fum'])
>>> a, b, [c, d] = list_and_vars()
>>> a, b, c, d
('fee', 'fi', 'fo', 'fum')

Answer 3

def funcOne():
    f2x,f2y = funcTwo() #tuple unpacking var1,var2 = (val1,val2)
    print a,b,list((lf2x,f2y)) #convert tuple to list

def funcTwo(): 
    return x, y #actually returns (x,y)

If we look at the following

def funcTwo():
    return 'a','b'
print(funcTwo())

We can see that funcTwo returns a tuple containing 'a','b' :

>>> 
('a', 'b')

In this way Python does only return one value, however it's tuple unpacking can make it look like this isn't the case:

var1,var2 = funcTwo()
print(var1)
print(var2)
>>> 
a
b

You could return a list explicitly:

def funcTwo():
    return ['a','b']
print(funcTwo())

In which case you are still returning one value, it's simply a list. For example:

def funcTwo():
    return ['a','b']
def funcOne():
    return 'c','d',funcTwo()
print(funcOne())

Would print

>>> 
('c', 'd', ['a', 'b'])

Again you can see, we've only returned one value, a tuple which consists of all the values we desired to return.

If you wanted to simply print something in funcOne unless you used string formatting you would get the same result as if you had print -ed the return values because print('a','b','c') prints ('a','b','c') however you could do something like:

def funcOne():
    print(','.join(['c','d',funcTwo().__repr__()]))
>>> 
c,d,['a', 'b']