Why is (a,b) equal to 22?

Question

a=1
b=a+1
a,b =2, a+1
print(a,b)
Solution: 22

a = 1, so b = 1+1= 2
a,b = 2, a+1
# 1, 2 = 2 ,1+1
#So solution should be 1,2,2,2? Why is it just 22? Any help appreciated:)

Answer 1

Python allows you to do multiple assignments in one step. Instead of

a = 1
b = 2
c = 3

, you can just do:

a, b, c = 1, 2, 3

Assignments are done from the right to the left, so the third value after the = (3) will be assigned to the third variable (c), the second value (2) to the second variable (b) and so on.

So a, b = 2, a + 1 will first set b to a + 1 (which is 2) and then set a to 2. The value of a is only changed once.

This syntax is particularly useful if you want to assign values of a list/tuple etc. to variables:

l = [1, 2, 3] # list with three elements

a, b, c = l

This will assign 1 to a, 2 to b and 3 to c.

Answer 2

Because python takes everything in sequence. So
a =1
/*simplified*/ a=2,b =early value of a (1) +1=2
So 22 is the output due to no space

Answer 3

You can ignore the second line, b=a+1, because b will be redefined in the next line.

a, b = 2, a+1 means:
b = a+1
a = 2

a was 1 before (see first line), so now both a and b are 2.

print(a, b) prints the values of a and b, separated by a space: 2 2

A variable can only have one value at a time.

a = 1 # a is 1
a = 2 # now a is 2, the previous value (1) is lost
a += 1 # now a is 3 (same as a = a + 1)
a = 'hello' # now a is something entirely different

Answer 4

Thanks, Anna and Mishra:).

So, what youre saying, is that on line 3 "(a,b =2, a+1)" a actually changes value 2 times?

From 1, to 2 (as Anna kindly listed above)?

Thanka for your help. I think I can see my mistake now.

Answer 5

Thanks for your help. Still not quite clear though.

I can see how b would be "22".
But the two numbers assigned to the value of "a" are "1" and "2". Where is the comman to make the "1" a "2"?

Thanks:).

Answer 6

Thanks so much Anna! I really appreciate it. 👍🏻