Working with multiple return values

[dshimer]

In the simplest terms...
I have a function that returns 3 values

>>> def sendnum():
...     return 1,2,3

and a function that takes 3 arguments.

>>> def receive(a=4,b=5,c=6):
...     print a,b,c

They of course do their individual jobs

>>> sendnum()
(1, 2, 3)
>>> receive(11,12,13)
11 12 13

Is there any way to code this so that the sending function doesn't send it as a list, or that the receiving function sees it as 3 different values? So instead of

>>> receive(sendnum())
(1, 2, 3) 5 6

I would get

 >>> receive(sendnum())
1 2 3

[bvdet]

In the simplest terms...
I have a function that returns 3 values

>>> def sendnum():
...     return 1,2,3

and a function that takes 3 arguments.

>>> def receive(a=4,b=5,c=6):
...     print a,b,c

They of course do their individual jobs

>>> sendnum()
(1, 2, 3)
>>> receive(11,12,13)
11 12 13

Is there any way to code this so that the sending function doesn't send it as a list, or that the receiving function sees it as 3 different values? So instead of

>>> receive(sendnum())
(1, 2, 3) 5 6

I would get

 >>> receive(sendnum())
1 2 3

>>> receive(*sendnum())
1 2 3
>>> 

[dshimer]

Fantastic, what is terminology for this, so I can study up on it? I have tried it in an system which embeds python to access CAD functions, so I have no control over the supplied objects. This works perfect.

Thanks

>>> receive(*sendnum())
1 2 3
>>> 

[bvdet]

Fantastic, what is terminology for this, so I can study up on it? I have tried it in an system which embeds python to access CAD functions, so I have no control over the supplied objects. This works perfect.

Thanks

A function can accept a variable number of arguments if an asterisk (*) precedes the last argument in an argument list:

>>> def sample(s, *args):
...     print s
...     for item in args:
...         print item
...         
>>> s = 'A string'
>>> sample(s, 'This', 'is', 'a', 'test')
A string
This
is
a
test
>>> aList = ('This', 'is', 'a', 'test')
>>> sample(s, aList)
A string
('This', 'is', 'a', 'test')
>>> sample(s, *aList)
A string
This
is
a
test
>>> 

A function can also accept a variable number of keyword arguments if '**' precedes the last argument in an argument list:

>>> def samplekw(**kargs):
...     for key in kargs:
...         print key, kargs[key]
...         
>>> samplekw(**{'key1': 1, 'key2': 100})
key2 100
key1 1
>>> samplekw(key1=1, key2=100)
key2 100
key1 1
>>> 

Combined:

>>> def sample(s, *args, **kargs):
...     print s
...     for item in args:
...         print item
...     for key in kargs:
...         print key, kargs[key]
...         
>>> sample(s, *aList, **{'key1': 1, 'key2': 100})
A string
This
is
a
test
key2 100
key1 1
>>> 

[bartonc]

Fantastic, what is terminology for this, so I can study up on it? I have tried it in an system which embeds python to access CAD functions, so I have no control over the supplied objects. This works perfect.

Thanks

Mark Lutz calls it "varargs" on p 338 of

7. More argument matching examples. Here is the sort of interaction you should get, along with comments that explain the matching that goes on:

def f1(a, b): print a, b             # normal args
 
def f2(a, *b): print a, b            # positional varargs
 
 f3(a, **b): print a, b           # keyword varargs
 
 f4(a, *b, **c): print a, b, c    # mixed modes
 
 f5(a, b=2, c=3): print a, b, c   # defaults
 
 f6(a, b=2, *c): print a, b, c    # defaults + positional varargs
% python
>>> f1(1, 2)                  # matched by position (order matters)
1 2
>>> f1(b=2, a=1)              # matched by name (order doesn't matter)
1 2
>>> f2(1, 2, 3)               # extra positionals collected in a tuple
1 (2, 3)
>>> f3(1, x=2, y=3)           # extra keywords collected in a dictionary
1 {'x': 2, 'y': 3}
>>> f4(1, 2, 3, x=2, y=3)     # extra of both kinds
1 (2, 3) {'x': 2, 'y': 3}