Why is classic if writing and inline if writing are not behaving the same way?-CodePudding

I got this code

firstId = True
       
for x in [1,2,3,4,5]:
    firstId = False if firstId else print(str(x)  " "   str(firstId))
    
print ("What is happening here ???")

firstId = True
       
for x in [1,2,3,4,5]:
    if firstId: 
        firstId = False
    else:
        print(str(x)  " "   str(firstId))

And strangly i have this output

2 False
3 None
4 None
5 None
What is happening here ???
2 False
3 False
4 False
5 False

From my understanding both if statement should behave the same way.But the boolean is not. I can't understand why the boolean somehow becomes None. Can someone explain what is happening?

CodePudding user response：

This:

firstId = False if firstId else print(str(x)  " "   str(firstId))

is the same as

firstId = (False if firstId else print(str(x)  " "   str(firstId)))

i.e.

if firstId:
    firstId = False
else:
    firstId = print(str(x)  " "   str(firstId))

It always assigns a value to firstId, and the conditional expression on the right determines what that value is.

In the else case, the value is None, because print(...) returns None.

A conditional expression is not a one-line if statement. It is a different construction for a different purpose.