问题
N = [1, 2, 3]
print(n for n in N)
results:
<generator object <genexpr> at 0x000000000108E780>
why this code couldn't print:
1
2
3
However the code:
sum(n for n in N)
could sum up all the number in N.
Could you please tell me why sum() could work but print() faild?
回答1:
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 list
or
print(*(n for n in N), sep='\n') # Again, unpacks values
or
print('\n'.join(map(str, n for n in N)))
or if you like comprehensions:
[print(n) for n in N]
You have to be aware that the last method constructs a list filled with None.
回答2:
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
回答3:
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
来源：https://stackoverflow.com/questions/44616012/how-to-print-the-content-of-the-generator