Python, tuple arguments playing nicely with others

Question

For example:

mytuple = ("Hello","World")
def printstuff(one,two,three):
    print one,two,three

printstuff(mytuple," How are you")

This naturally crashes out with a TypeError because I'm only giving it two arguments when it expects three.

Is there a simple way of effectively 'splitting' a tuple in a tider way than expanding everything? Like:

printstuff(mytuple[0],mytuple[1]," How are you")

score 6 · Answer 1 · answered Mar 28 '11 at 20:53

Kinda,... you can do this:

>>> def fun(a, b, c):
...     print(a, b, c)
...
>>> fun(*(1, 2), 3)
  File "<stdin>", line 1
SyntaxError: only named arguments may follow *expression
>>> fun(*(1, 2), c=3)
1 2 3

As you can see, you can do what you want pretty much as long as you qualify any argument coming after it with its name.

score 4 · Accepted Answer · answered Mar 28 '11 at 20:50

Not without changing the argument ordering or switching to named parameters.

Here's the named parameters alternative.

printstuff( *mytuple, three=" How are you" )

Here's the switch-the-order alternative.

def printstuff( three, one, two ):
    print one, two, three

printstuff( " How are you", *mytuple )

Which may be pretty terrible.

score 3 · Answer 3 · answered Mar 28 '11 at 20:48

3

Try the following:

printstuff(*(mytuple[0:2]+(" how are you",)))

answered Mar 28 '11 at 20:48

yan

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To match the arity in the original example. – yan Mar 29 '11 at 02:31
4

But `mytuple` is already a 2-tuple. So you're slicing a 2-tuple (effectively copying it) for no apparent reason. – ncoghlan Mar 29 '11 at 03:14

score 1 · Answer 4 · answered May 05 '12 at 15:15

1

mytuple = ("Hello","World")

def targs(tuple, *args):
    return tuple + args

def printstuff(one,two,three):
    print one,two,three 

printstuff(*targs(mytuple, " How are you"))
Hello World  How are you

answered May 05 '12 at 15:15

Derek Litz

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score 0 · Answer 5 · answered Jun 05 '17 at 17:25

Actually, it is possible to do it without changing the order of the arguments. First you have to transform your string to a tuple, add it to your tuple mytuple and then pass your larger tuple as argument.

printstuff(*(mytuple+(" How are you",)))
# With your example, it returns: "Hello World  How are you"

score 0 · Answer 6 · answered Mar 28 '11 at 20:49

0

You could try:

def printstuff(*args):
    print args

Another option is to use the new namedtuple collections type.

answered Mar 28 '11 at 20:49

rlotun

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But `args` would be (("hello","world)," how are you") as tuple and string. – S.Lott Mar 28 '11 at 20:51

Python, tuple arguments playing nicely with others

6 Answers6