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Python: next() function returns unexpected 'None'

it's my first question ever so I'll try to be as clear as I can. I noticed the next() functions and it seems a more elegant solution to use than the classical nested loop. So I run a simple code:

liste=['foo','bar','baz']

try:
    G= (print(x) for x in liste)
    print(next(G))
    print(next(G))
    print(next(G))
    print(next(G))

except StopIteration:
    print("That was obviously expected")

And I'm expecting:

foo
bar
baz
That was obviously expected

to appear on my screen, but instead I got:

foo
None
bar
None
baz
None
That was obviously expected

So my question(s) is simple:

Why are there None responses after run ?

What is the good way and when is it the good moment to use next() ?

Thanks

Solution

  • Because print() returns None.

    You are essentially doing print(print(..)). The inner print prints as you would expect ('foo', ...) but the outer prints the print which is where the None comes from.