Python iteration? Why code1 != code2

Question

#code 1
x=2
x,x=x+3, x+4
print(x)

#code 2
x=2
x=x+3
x=x+4
print(x)

Answer 1

In code1 x+3 doesn't apply until after x+4. so we'll have x=x+4=> x=6. This is a rule in such situations. For example:
x, y = y, x
In the above if x=y be applied first then no swap will be taken effect and both variables will be equal to primary value of y.

Answer 2

Thanks for your answer, Qasem!

Answer 3

HI there Storm,

#code 1 = 6
#code 2 = 9
Working out the result of #code 2 manually was no problem. How exactly line 3 of #code 1 is calculated I'm not sure. I use a tool on Python Tutor frequently to visualise how code works. You may find it useful in the future:

Try plugin your code into this tool:

http://pythontutor.com/visualize.html#mode=edit

and let me know how you get on

Answer 4

Thank you Stuart, very useful tool.