CODEWITHSUNDEEP
python
asdfg
asdfg

Reputation: 31

what does 'can't assign to literal' mean python?

x=10, y=20

This is really short code, but when I execute this code in python, "can't assign to literal" error appears. Of course I know that this can't be executed in pyhon just intuitively, and it's out of question. This code should be changed to 

x,y=10,20

or 

x=10
y=20

like this. but I can't explain WHY the first code is error logically. please help me!

Upvotes: 3

Views: 239

Answers (2)

Ender Look
Ender Look

Reputation: 2391

What python does with this:

A, B = C, D

It assigns the first value to the first variable, and the second value to the second variable:

A = C
B = D

This works because python internally makes "tuples" with your values delimited by a comma:

(A, B) = (C, D)

When you do

A = C, B = D

Python believes that you are doing:

A = (C, B) = D

Or:

(C, B) = D   # Which is C = D[0] and B = D[1]
A = (C, B)

But C in you case is a number, not a variable, so:

x = 10, y = 20

Is:

x = (10, y) = 20

Or:

(10, y) = 20
x = (10, y)

Which is not possible. You can't assign something to a number (10). Doing 10 = 'something' will give you SyntaxError: can't assign to literal.

To make simpler, just execute in your python console:

10 = 1

And you will have the same error.

Upvotes: 0

John Zwinck
John Zwinck

Reputation: 249123

Your error is that you think x=10, y=20 means x=10; y=20 when in fact it means x=(10, y)=20. This is because the comma creates a tuple, and you can't assign to a tuple which contains a literal (in this case 10).

Upvotes: 6

Related Questions