Python can't define tuples in a function

Question

For some reason in python everytime I try to define tuples in a function I get a syntax error. For example I have a function that adds vectors to the program, it looks like this:

def add_vectors((angle_1, l_1),(angle_2, l_2)):
    x=math.sin(angle1)*l_1+math.sin(angle2)*l_2
    y=math.cos(angle1)*l_1+math.cos(angle2)*l_2

    angle=0.5*math.pi-math.atan2(y, x)
    length=math.hypot(x, y)
    return (angle, length)

Which seems alright, but the interpretor says there is a syntax error and highlights the first bracket of the first tuple. I am using Python 3.2.3. What am I doing wrong?

Tuples in function argument lists are not allowed in Python 3. — BrenBarn, Nov 17 '13 at 20:15

score 23 · Accepted Answer · edited Jun 09 '20 at 19:01

Tuple parameters are no longer supported in Python3: http://www.python.org/dev/peps/pep-3113/

You may unpack your tuple at the beginning of your function:

def add_vectors(v1, v2):
    angle_1, l_1 = v1
    angle_2, l_2 = v2
    x=math.sin(angle1)*l_1+math.sin(angle2)*l_2
    y=math.cos(angle1)*l_1+math.cos(angle2)*l_2

    angle=0.5*math.pi-math.atan2(y, x)
    length=math.hypot(x, y)
    return (angle, length)

score 1 · Answer 2 · answered Nov 17 '13 at 20:16

1

There is no syntax for such tuple unpacking. Instead, take two tuples as arguments on their own and then unpack them into separate arguments.

def add_vectors(tup1, tup2):
    angle_1, l_1 = tup1
    angle_2, l_2 = tup2
    ...

answered Nov 17 '13 at 20:16

justinas

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Python can't define tuples in a function

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