CODEWITHSUNDEEP
pythongenerator
chentaocuc
chentaocuc

Reputation: 177

How to print the content of the generator?

N = [1, 2, 3]
print(n for n in N)

Results:

<generator object <genexpr> at 0x000000000108E780>

Why didn't it print?:

1
2
3

However the code:

sum(n for n in N)

Will sum up all the number in N.

Could you please tell me why sum() worked but print() failed?

Upvotes: 7

Views: 19918

Answers (4)

Szymon
Szymon

Reputation: 510

It's because you passed a generator to a function and that's what __repr__ method of this generator returns. If you want to print what it would generate, you can use:

print(*N, sep='\n') # * will unpack the generator

or

print('\n'.join(map(str, N)))

Note that once you retrieve the generator's output to print it, the generator is exhausted - trying to iterate over it again will produce no items.

Upvotes: 15

sameer_nubia
sameer_nubia

Reputation: 811

Generator …

def  genfun():
    yield ‘A’
    yield ‘B’
    yield ‘C’
g=genfun()
print(next(g))= it will print 0th index .
print(next(g))= it will print 1st index.
print(next(g))= it will print 2nd index.
print(next(g))= it will print 3rd index But here in this case it will give Error as 3rd element is not there 
So , prevent from this error we will use for loop as below .
 for  i in g :
    print(i)

Upvotes: -1

OneCricketeer
OneCricketeer

Reputation: 191733

You are literally printing a generator object representation

If you want on one line, try printing a list 

print([n for n in N])

Which is just print(N)

If you want a line separated string, print that

print("\n".join(map(str, N)))

Or write a regular loop and don't micro optimize the lines of code

Upvotes: 2

Charles Clayton
Charles Clayton

Reputation: 17946

If you don't want to cast it as a list, you can try:

print(*(n for n in N))

See: https://docs.python.org/3/tutorial/controlflow.html#tut-unpacking-arguments

Upvotes: 2

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