CODEWITHSUNDEEP
python
Jeff
Jeff

Reputation: 12418

Commas in a Python math argument

I noticed by accident that Python's primitive math operators support commas in both numeric arguments. A tuple is returned. What is it doing and why is this syntax supported?

Here are a few examples:

>>> 2,10,2 / 2
(2, 10, 1)

>>> 2,10,2 * 2
(2, 10, 4)

>>> 2,10,2 % 2,3
(2, 10, 0, 3)

Upvotes: 2

Views: 1214

Answers (4)

jtagle
jtagle

Reputation: 302

You are just defining a tuple, it's not that math operators supports commas. What python is doing there, is assuming you are doing a tuple (because of the commas), so it evaluate each value between the comas, and then store it to the tuple. Not a thing about primitive math operator, it's just how python interprets commas. You could do 1,"a","a"+"b",2+5, and that would give you the tuple (1, "a", "ab", 7).

An easy and simplist way of giving an answer is: If python finds a comma in your code, it assumes you put it there for separating data. Then, if he finds 1, 1+1, you are giving two data, a number one, and an expresion 1+1. Python evaluates the expresion and says "Oh, its 2". Then, he returns you the (1,2) tuple.

Im not an expert at python compiler, so don't rely 100% on my answer, but I'm quite sure that's the reason.

Upvotes: 0

mageliz
mageliz

Reputation: 146

You are actually using a tuple (which is why the output is surrounded by the parenthesis.) The math is only happening on one element of the tuple.

https://docs.python.org/3/tutorial/datastructures.html#tuples-and-sequences

Upvotes: 1

Prune
Prune

Reputation: 77837

This is especially visible in interactive mode. Python semantics turn a comma-separated sequence into a tuple. This underlies the "tuple unpacking" you know from function returns, such as

value, status = my_func(args)

If you write

a, b, c = 1, 2, 3

You get the corresponding assignments just as if you'd put (1, 2, 3) on the RHS. Similarly,

a = 1, 2, 3

Gets you an a value of the entire tuple, (1, 2, 3).

Note that you need an all-or-none approach: one variable on the LHS, or exactly the correct quantity for the tuple length.

Upvotes: 0

heemayl
heemayl

Reputation: 42007

In 2,10,2 / 2, the operation performed actually is:

2, 10, (2 / 2)

Hence you get the (2, 10, 1) as output.

In Python, tuples are actually a collection of values separated by commas, the surrounding parentheses are to avoid ambiguity.

Upvotes: 11

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