I'd like to use a walrus operator with a simple generator in a while loop
def gen():
for i in range(5):
yield i
yield 10
g = gen()
while i := next(g):
print(i)
I expect the output to be:
0
1
2
3
4
10
However it's not printing anything. I'm aware I can do this in a for loop:
for i in gen():
print(i)
I'm not interested in the output being exact. I want a simple example of using generators with walrus operators.
This loop:
while i := next(g):
print(i)
will iterate through each element of your generator and print it, until one of them is falsey. Since your generator emits 0 as its first element, the while condition is immediately false, and the loop ends without printing.
But if, for example, your iterator was:
g = iter([2,1,0,2,5])
then your loop would print 2 and 1, and stop when it received the value 0.
If you want to iterate through all the elements until it runs out of elements, just use:
for i in g:
print(i)
gen() is returning 0 on the first iteration. range(1, 5) to set range to go from 1 to 5. I also updated 10 to None else the generator runs out and throws Ex
def gen():
for i in range(1, 5):
yield i
yield None
g = gen()
while i := next(g):
print(i)
output:
1
2
3
4
Process finished with exit code 0
Because you are using a while loop you need the condition to be True. The first element that is returned is 0. Which is interpreted as False.
If you need the := operator, use:
try:
while (i := next(g)) or i == 0:
print(i)
except StopIteration:
# This executes when the generator is exhausted
pass
Or use range(1, 10), so 0 is never returned
If you are open to changes, please use:
for i in g:
print(i)
Or you avoid the removal of g's assignment, and do:
for i in gen():
print(i)
0, 10
gen()is zero, so the while condition is immediately false, and the loop ends.for i in g: print(i).