Round Bracket inside Round Bracket in Def Function

Question

I am doing a pygame physics tutorial. However, when I try putting Round Bracket inside Round Bracket in Def Function, it says "Invalid Syntax". I could not find a answer anywhere.

def addVectors((angle1, length1), (angle2, length2)):

Answer 1

That only works in Python 2 sadly:

>$ python2
Python 2.7.18 (default, Mar  8 2021, 13:02:45) 
[GCC 9.3.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> def addVectors((angle1, length1), (angle2, length2)):
...   pass
... 
>>> 
>$ python3
Python 3.8.8 (default, Apr 13 2021, 19:58:26) 
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> def addVectors((angle1, length1), (angle2, length2)):
  File "<stdin>", line 1
    def addVectors((angle1, length1), (angle2, length2)):
                   ^
SyntaxError: invalid syntax

I suggest using a namedtuple :

from collections import namedtuple

Vector = namedtuple('Vector', ['angle', 'length'])

v1 = Vector(angle=1, length=1)
v2 = Vector(angle=2, length=1)

def addVectors(v1, v2):
    return Vector(v1.angle + v2.angle, v1.length + v2.length)

Answer 2

You are trying to pass a tuple by parameter but this way is the wrong syntax way. Try something like that:

def addVectors(*angles):
    for i in angles:
        print(i)

# addVectors((angle1, length1), (angle2, length2))
# (1, 2)
# (3, 4)

The * will unpack like a list and you can pass any size of parameters

Answer 3

Given your specific example, you can hopefully see why the syntax you are looking for is error prone. Imagine what happens when you accidentally mess up a single parenthesis 6 months from now. You have a couple of options to implement the same functionality trivially in Python 3 with fewer parentheses.

If you want the input to be four objects:

def addVectors(angle1, length1, angle2, length2):
    ...

and call as

self.angle, self.speed = addVectors(self.angle, self.speed, *gravity)

If you want two inputs, you can specify an explicit unpacking:

def addVectors(
    angle1, length1 = vector1
    angle2, length2 = vector2
    ...

and call it as

self.angle, self.speed = addVectors((self.angle, self.speed), gravity)

As you can see, there's no reason to give up on Python 3 just because of this syntax.